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| 1 : | root | 1 | This is unix.info, produced by makeinfo version 4.0 from unix.texinfo. |
| 2 : | |||
| 3 : | |||
| 4 : | File: unix.info, Node: Regular expressions, Next: Nested shells and reverse apostrophes, Prev: Wildcards, Up: Shells | ||
| 5 : | |||
| 6 : | Regular expressions | ||
| 7 : | ------------------- | ||
| 8 : | |||
| 9 : | The wildcards belong to the shell. They are used for matching | ||
| 10 : | filenames. UNIX has a more general and widely used mechanism for | ||
| 11 : | matching _strings_, this is through _regular expressions_. | ||
| 12 : | |||
| 13 : | Regular expressions are used by the `egrep' utility, text editors | ||
| 14 : | like `ed', `vi' and `emacs' and `sed' and `awk'. They are also used in | ||
| 15 : | the C programming language for matching input as well as in the Perl | ||
| 16 : | programming language and `lex' tokenizer. Here are some examples using | ||
| 17 : | the `egrep' command which print lines from the file `/etc/rc' which | ||
| 18 : | match certain conditions. The `' contruction is part of `egrep'. | ||
| 19 : | Everything in between these symbols is a regular expression. Notice that | ||
| 20 : | special shell symbols `! * &' have to be preceded with a backslash `\' | ||
| 21 : | in order to prevent the shell from expanding them! | ||
| 22 : | |||
| 23 : | |||
| 24 : | # Print all lines beginning with a comment # | ||
| 25 : | |||
| 26 : | egrep '(^#)' /etc/rc | ||
| 27 : | |||
| 28 : | # Print all lines which DON'T begin with # | ||
| 29 : | |||
| 30 : | egrep '(^[^#])' /etc/rc | ||
| 31 : | |||
| 32 : | # Print all lines beginning with e, f or g. | ||
| 33 : | |||
| 34 : | egrep '(^[efg])' /etc/rc | ||
| 35 : | |||
| 36 : | # Print all lines beginning with uppercase | ||
| 37 : | |||
| 38 : | egrep '(^[A-Z])' /etc/rc | ||
| 39 : | |||
| 40 : | # Print all lines NOT beginning with uppercase | ||
| 41 : | |||
| 42 : | egrep '(^[^A-Z])' /etc/rc | ||
| 43 : | |||
| 44 : | # Print all lines containing ! * & | ||
| 45 : | |||
| 46 : | egrep '([\!\*\&])' /etc/rc | ||
| 47 : | |||
| 48 : | # All lines containing ! * & but not starting # | ||
| 49 : | |||
| 50 : | egrep '([^#][\!\*\&])' /etc/rc | ||
| 51 : | |||
| 52 : | Regular expressions are made up of the following `atoms'. | ||
| 53 : | |||
| 54 : | These examples assume that the file `/etc/rc' exists. If it doesn't | ||
| 55 : | exist on the machine you are using, try to find the equivalent by, for | ||
| 56 : | instance, replacing `/etc/rc' with `/etc/rc*' which will try to find a | ||
| 57 : | match beginning with the rc. | ||
| 58 : | |||
| 59 : | `.' | ||
| 60 : | Match any single character except the end of line. | ||
| 61 : | |||
| 62 : | `^' | ||
| 63 : | Match the beginning of a line as the first character. | ||
| 64 : | |||
| 65 : | `$' | ||
| 66 : | Match end of line as last character. | ||
| 67 : | |||
| 68 : | `[..]' | ||
| 69 : | Match any character in the list between the square brackets.(see | ||
| 70 : | below). | ||
| 71 : | |||
| 72 : | `*' | ||
| 73 : | Match zero or more occurrances of the preceding expression. | ||
| 74 : | |||
| 75 : | `+' | ||
| 76 : | Match one or more occurrences of the preceding expression. | ||
| 77 : | |||
| 78 : | `?' | ||
| 79 : | Match zero or one occurrance of the preceding expression. | ||
| 80 : | |||
| 81 : | You can find a complete list in the unix manual pages. The square | ||
| 82 : | brackets above are used to define a _class_ of characters to be | ||
| 83 : | matched. Here are some examples, | ||
| 84 : | |||
| 85 : | * If the square brackets contain a list of characters, $[a-z156]$ | ||
| 86 : | then a single occurrance of any character in the list will match | ||
| 87 : | the regular expression: in this case any lowercase letter or the | ||
| 88 : | numbers 1, 5 and 6. | ||
| 89 : | |||
| 90 : | * If the first character in the brackets is the caret symbol `^' | ||
| 91 : | then any character _except_ those in the list will be matched. | ||
| 92 : | |||
| 93 : | * Normally a dash or minus sign `-' means a range of characters. If | ||
| 94 : | it is the first character after the `[' or after `[^' then it is | ||
| 95 : | treated literally. | ||
| 96 : | |||
| 97 : | |||
| 98 : | File: unix.info, Node: Nested shells and reverse apostrophes, Prev: Regular expressions, Up: Shells | ||
| 99 : | |||
| 100 : | Nested shell commands and " | ||
| 101 : | --------------------------- | ||
| 102 : | |||
| 103 : | The backwards apostrophes `...` can be used in all shells and also in | ||
| 104 : | the programming language Perl. When these are encountered in a string | ||
| 105 : | the shell tries to execute the command inside the quotes and replace | ||
| 106 : | the quoted expression by the result of that command. For example: | ||
| 107 : | unix% echo "This system's kernel type is `/bin/file /vmunix`" | ||
| 108 : | This system's kernel type is /vmunix: sparc executable not stripped | ||
| 109 : | |||
| 110 : | unix% foreach file ( `ls /etc/rc*` ) | ||
| 111 : | ? echo I found a config file $file | ||
| 112 : | ? echo Its type is `/bin/file $file` | ||
| 113 : | ? end | ||
| 114 : | |||
| 115 : | I found a config file /etc/rc | ||
| 116 : | Its type is /etc/rc: executable shell script | ||
| 117 : | I found a config file /etc/rc.boot | ||
| 118 : | Its type is /etc/rc.boot: executable shell script | ||
| 119 : | I found a config file /etc/rc.ip | ||
| 120 : | Its type is /etc/rc.ip: executable shell script | ||
| 121 : | I found a config file /etc/rc.local | ||
| 122 : | Its type is /etc/rc.local: ascii text | ||
| 123 : | I found a config file /etc/rc.local~ | ||
| 124 : | Its type is /etc/rc.local~: ascii text | ||
| 125 : | I found a config file /etc/rc.single | ||
| 126 : | Its type is /etc/rc.single: executable shell script | ||
| 127 : | I found a config file /etc/rc~ | ||
| 128 : | Its type is /etc/rc~: executable shell script | ||
| 129 : | |||
| 130 : | This is how we insert the result of a shell command into a text | ||
| 131 : | string or variable. | ||
| 132 : | |||
| 133 : | |||
| 134 : | File: unix.info, Node: UNIX command overview, Next: Terminals, Prev: Shells, Up: The login environment | ||
| 135 : | |||
| 136 : | UNIX command overview | ||
| 137 : | ===================== | ||
| 138 : | |||
| 139 : | * Menu: | ||
| 140 : | |||
| 141 : | * Keys:: | ||
| 142 : | * Alternative shells:: | ||
| 143 : | * terminal emulators:: | ||
| 144 : | * Remote login:: | ||
| 145 : | * Text editors:: | ||
| 146 : | * File handling:: | ||
| 147 : | * File browsers:: | ||
| 148 : | * Access control:: | ||
| 149 : | * Extracting from files:: | ||
| 150 : | * Locating files:: | ||
| 151 : | * Disk usage:: | ||
| 152 : | * Other users:: | ||
| 153 : | * Contacting users:: | ||
| 154 : | * Mail:: | ||
| 155 : | * File transfer:: | ||
| 156 : | * Compilers:: | ||
| 157 : | * Interpreted languages:: | ||
| 158 : | * System statistics:: | ||
| 159 : | * System identity:: | ||
| 160 : | * Internet resources:: | ||
| 161 : | * Text/postscript:: | ||
| 162 : | * Pictures/graphics:: | ||
| 163 : | * Miscellaneous:: | ||
| 164 : | |||
| 165 : | |||
| 166 : | File: unix.info, Node: Keys, Next: Alternative shells, Prev: UNIX command overview, Up: UNIX command overview | ||
| 167 : | |||
| 168 : | Important keys | ||
| 169 : | -------------- | ||
| 170 : | |||
| 171 : | <CTRL-A> | ||
| 172 : | Jump to start of line. If `screen' is active, this prefixes all | ||
| 173 : | control key commands for `screen' and then the normal `CTRL-A' is | ||
| 174 : | replaced by `CTRL-a a'. | ||
| 175 : | |||
| 176 : | <CTRL-C> | ||
| 177 : | Interrupt or break key. Sends signal 15 to a process. | ||
| 178 : | |||
| 179 : | <CTRL-D> | ||
| 180 : | Signifies `EOF' (end of file) or shows expansion matches in | ||
| 181 : | command/filename completion *Note Command/filename completion::. | ||
| 182 : | |||
| 183 : | <CTRL-E> | ||
| 184 : | Jump to end of line. | ||
| 185 : | |||
| 186 : | <CTRL-L> | ||
| 187 : | Clear screen in newer shells and in emacs. Same as `clear' in the | ||
| 188 : | shell. | ||
| 189 : | |||
| 190 : | <CTRL-Z> | ||
| 191 : | Suspend the present process, but do not destroy it. This sends | ||
| 192 : | signal 18 to the process. | ||
| 193 : | |||
| 194 : | |||
| 195 : | File: unix.info, Node: Alternative shells, Next: terminal emulators, Prev: Keys, Up: UNIX command overview | ||
| 196 : | |||
| 197 : | Alternative shells | ||
| 198 : | ------------------ | ||
| 199 : | |||
| 200 : | `bash' | ||
| 201 : | The Bourne Again shell, an improved sh. | ||
| 202 : | |||
| 203 : | `csh' | ||
| 204 : | The standard C-shell. | ||
| 205 : | |||
| 206 : | `jsh' | ||
| 207 : | The same as sh, with C-shell style job control. | ||
| 208 : | |||
| 209 : | `ksh' | ||
| 210 : | The Korn shell, an improved sh. | ||
| 211 : | |||
| 212 : | `sh' | ||
| 213 : | The original Bourne shell. | ||
| 214 : | |||
| 215 : | `sh5' | ||
| 216 : | On ULTRIX systems the standard Bourne shell is quite stupid. sh5 | ||
| 217 : | corresponds to the normal Bourne shell on these systems. | ||
| 218 : | |||
| 219 : | `tcsh' | ||
| 220 : | An improved C-shell. | ||
| 221 : | |||
| 222 : | `zsh' | ||
| 223 : | An improved sh. | ||
| 224 : | |||
| 225 : | |||
| 226 : | File: unix.info, Node: terminal emulators, Next: Remote login, Prev: Alternative shells, Up: UNIX command overview | ||
| 227 : | |||
| 228 : | Window based terminal emulators | ||
| 229 : | ------------------------------- | ||
| 230 : | |||
| 231 : | `xterm' | ||
| 232 : | The standard X11 terminal window. | ||
| 233 : | |||
| 234 : | `shelltool, cmdtool' | ||
| 235 : | Openwindows terminals from Sun Microsystems. These are not | ||
| 236 : | completely X11 compatible during copy/paste operations. | ||
| 237 : | |||
| 238 : | `screen' | ||
| 239 : | This is not a window in itself, but allows you to emulate having | ||
| 240 : | several windows inside a single (say) xterm window. The user can | ||
| 241 : | switch between different windows and open new ones, but can only | ||
| 242 : | see one window at a time *Note Multiple screens::. | ||
| 243 : | |||
| 244 : | |||
| 245 : | File: unix.info, Node: Remote login, Next: Text editors, Prev: terminal emulators, Up: UNIX command overview | ||
| 246 : | |||
| 247 : | Remote shells and logins | ||
| 248 : | ------------------------ | ||
| 249 : | |||
| 250 : | `rlogin' | ||
| 251 : | Login onto a remote unix system. | ||
| 252 : | |||
| 253 : | `rsh' | ||
| 254 : | Open a shell on a remote system (require access rights). | ||
| 255 : | |||
| 256 : | `telnet' | ||
| 257 : | Open a connection to a remove system using the telnet protocol. | ||
| 258 : | |||
| 259 : | |||
| 260 : | File: unix.info, Node: Text editors, Next: File handling, Prev: Remote login, Up: UNIX command overview | ||
| 261 : | |||
| 262 : | Text editors | ||
| 263 : | ------------ | ||
| 264 : | |||
| 265 : | `ed' | ||
| 266 : | An ancient line-editor. | ||
| 267 : | |||
| 268 : | `vi' | ||
| 269 : | Visual interface to `ed'. This is the only "standard" unix text | ||
| 270 : | editor supplied by vendors. | ||
| 271 : | |||
| 272 : | `emacs' | ||
| 273 : | The most powerful UNIX editor. A fully configurable, user | ||
| 274 : | programmable editor which works under X11 and on tty-terminals. | ||
| 275 : | |||
| 276 : | `xemacs' | ||
| 277 : | A pretty version of emacs for X11 windows. | ||
| 278 : | |||
| 279 : | `pico' | ||
| 280 : | A tty-terminal only editor, comes as part of the PINE mail package. | ||
| 281 : | |||
| 282 : | `xedit' | ||
| 283 : | A test X11-only editor supplied with X-windows. | ||
| 284 : | |||
| 285 : | `textedit' | ||
| 286 : | A simple X11-only editor supplied by Sun Microsystems. | ||
| 287 : | |||
| 288 : | |||
| 289 : | File: unix.info, Node: File handling, Next: File browsers, Prev: Text editors, Up: UNIX command overview | ||
| 290 : | |||
| 291 : | File handling commands | ||
| 292 : | ---------------------- | ||
| 293 : | |||
| 294 : | `ls' | ||
| 295 : | List files in specified directory (like `dir' on other systems). | ||
| 296 : | |||
| 297 : | `cp' | ||
| 298 : | Copy files. | ||
| 299 : | |||
| 300 : | `mv' | ||
| 301 : | Move or rename files. | ||
| 302 : | |||
| 303 : | `touch' | ||
| 304 : | Creates an empty new file if none exists, or updates date and time | ||
| 305 : | stamps on existing files. | ||
| 306 : | |||
| 307 : | `rm, unlink' | ||
| 308 : | Remove a file or link (delete). | ||
| 309 : | |||
| 310 : | `mkdir, rmdir' | ||
| 311 : | Make or remove a directory. A directory must be empty in order to | ||
| 312 : | be able to remove it. | ||
| 313 : | |||
| 314 : | `cat' | ||
| 315 : | Concatenate or join together a number of files. The output is | ||
| 316 : | written to the standard output by default. Can also be used to | ||
| 317 : | simply print a file on screen. | ||
| 318 : | |||
| 319 : | `lp, lpr' | ||
| 320 : | Line printer. Send a file to the default printer, or the printer | ||
| 321 : | defined in the `PRINTER' evironment variable. | ||
| 322 : | |||
| 323 : | `lpq, lpstat' | ||
| 324 : | Show the status of the print queue. | ||
| 325 : | |||
| 326 : | |||
| 327 : | File: unix.info, Node: File browsers, Next: Access control, Prev: File handling, Up: UNIX command overview | ||
| 328 : | |||
| 329 : | File browsing | ||
| 330 : | ------------- | ||
| 331 : | |||
| 332 : | `more' | ||
| 333 : | Shows one screen full at a time. Possibility to search for a | ||
| 334 : | string and edit the file. This is like `type FILE | more' in DOS. | ||
| 335 : | |||
| 336 : | `less' | ||
| 337 : | An enhanced version of more. | ||
| 338 : | |||
| 339 : | `mc' | ||
| 340 : | Midnight commander, a free version of the `Norton Commander' PC | ||
| 341 : | utility for unix. (Only for non-serious UNIX users...) | ||
| 342 : | |||
| 343 : | `fmgr' | ||
| 344 : | A window based file manager with icons and all that nonsense. | ||
| 345 : | |||
| 346 : | |||
| 347 : | File: unix.info, Node: Access control, Next: Extracting from files, Prev: File browsers, Up: UNIX command overview | ||
| 348 : | |||
| 349 : | Ownership and granting access permission | ||
| 350 : | ---------------------------------------- | ||
| 351 : | |||
| 352 : | `chmod' | ||
| 353 : | Change file access mode. | ||
| 354 : | |||
| 355 : | `chown, chgrp' | ||
| 356 : | Change owner and group of a file. The GNU version of `chown' | ||
| 357 : | allows both these operations to be performed together using the | ||
| 358 : | syntax `chown OWNER.GROUP FILE'. | ||
| 359 : | |||
| 360 : | `acl' | ||
| 361 : | On newer Unices, Access control lists allow access to be granted | ||
| 362 : | on a per-user basis rather than by groups. | ||
| 363 : | |||
| 364 : | |||
| 365 : | File: unix.info, Node: Extracting from files, Next: Locating files, Prev: Access control, Up: UNIX command overview | ||
| 366 : | |||
| 367 : | Extracting from and rebuilding files | ||
| 368 : | ------------------------------------ | ||
| 369 : | |||
| 370 : | `cut' | ||
| 371 : | Extract a column in a table | ||
| 372 : | |||
| 373 : | `paste' | ||
| 374 : | Merge several files so that each file becomes a column in a table. | ||
| 375 : | |||
| 376 : | `sed' | ||
| 377 : | A batch text-editor for searching, replacing and selecting text | ||
| 378 : | without human intervention. | ||
| 379 : | |||
| 380 : | `awk' | ||
| 381 : | A prerunner to the Perl language, for extracting and modifying | ||
| 382 : | textfiles. | ||
| 383 : | |||
| 384 : | `rmcr' | ||
| 385 : | Strip carriage return (ASCII 13) characters from a file. Useful | ||
| 386 : | for converting DOS files to unix. | ||
| 387 : | |||
| 388 : | |||
| 389 : | File: unix.info, Node: Locating files, Next: Disk usage, Prev: Extracting from files, Up: UNIX command overview | ||
| 390 : | |||
| 391 : | Locating files | ||
| 392 : | -------------- | ||
| 393 : | |||
| 394 : | `find' | ||
| 395 : | Search for files from a specified directory using various criteria. | ||
| 396 : | |||
| 397 : | `locate' | ||
| 398 : | Fast search in a global file database for files containing a | ||
| 399 : | search-string. | ||
| 400 : | |||
| 401 : | `whereis' | ||
| 402 : | Look for a command and its documentation on the system. | ||
| 403 : | |||
| 404 : | |||
| 405 : | File: unix.info, Node: Disk usage, Next: Other users, Prev: Locating files, Up: UNIX command overview | ||
| 406 : | |||
| 407 : | Disk usage. | ||
| 408 : | ----------- | ||
| 409 : | |||
| 410 : | `du' | ||
| 411 : | Show number of blocks used by a file or files. | ||
| 412 : | |||
| 413 : | `df' | ||
| 414 : | Show the state of usage for one or more disk partitions. | ||
| 415 : | |||
| 416 : | |||
| 417 : | File: unix.info, Node: Other users, Next: Contacting users, Prev: Disk usage, Up: UNIX command overview | ||
| 418 : | |||
| 419 : | Show other users logged on | ||
| 420 : | -------------------------- | ||
| 421 : | |||
| 422 : | `users' | ||
| 423 : | Simple list of other users. | ||
| 424 : | |||
| 425 : | `finger' | ||
| 426 : | Show who is logged onto this and other systems. | ||
| 427 : | |||
| 428 : | `who' | ||
| 429 : | List of users logged into this system. | ||
| 430 : | |||
| 431 : | `w' | ||
| 432 : | Long list of who is logged onto this system and what they are | ||
| 433 : | doing. | ||
| 434 : | |||
| 435 : | |||
| 436 : | File: unix.info, Node: Contacting users, Next: Mail, Prev: Other users, Up: UNIX command overview | ||
| 437 : | |||
| 438 : | Contacting other users | ||
| 439 : | ---------------------- | ||
| 440 : | |||
| 441 : | `write' | ||
| 442 : | Send a simple message to the named user, end with <CTRL-D>. The | ||
| 443 : | command `mesg n' switches off messages receipt. | ||
| 444 : | |||
| 445 : | `talk' | ||
| 446 : | Interactive two-way conversation with named user. | ||
| 447 : | |||
| 448 : | `irc' | ||
| 449 : | Internet relay chat. A conferencing system for realtime multi-user | ||
| 450 : | conversations, for addicts and losers. | ||
| 451 : | |||
| 452 : | |||
| 453 : | File: unix.info, Node: Mail, Next: File transfer, Prev: Contacting users, Up: UNIX command overview | ||
| 454 : | |||
| 455 : | Mail senders/readers | ||
| 456 : | -------------------- | ||
| 457 : | |||
| 458 : | `mail' | ||
| 459 : | The standard (old) mail interface. | ||
| 460 : | |||
| 461 : | `Mail' | ||
| 462 : | Another mail interface. | ||
| 463 : | |||
| 464 : | `elm' | ||
| 465 : | Electronic Mail program. Lots of functionality but poor support | ||
| 466 : | for multimedia. | ||
| 467 : | |||
| 468 : | `pine' | ||
| 469 : | Rumours (untrue) are that pine stands for Pine is Not Elm; it | ||
| 470 : | actually stands for nothing at all. Improved support for | ||
| 471 : | multimedia but very slow and rather stupid at times. Some of the | ||
| 472 : | best features of elm have been removed! | ||
| 473 : | |||
| 474 : | `mailtool' | ||
| 475 : | Sun's openwindows client program. | ||
| 476 : | |||
| 477 : | `rmail' | ||
| 478 : | A mail interface built into the emacs editor. | ||
| 479 : | |||
| 480 : | `netscape mail' | ||
| 481 : | A mail interface built into the netscape navigator. | ||
| 482 : | |||
| 483 : | `zmail' | ||
| 484 : | A commerical mail package. | ||
| 485 : | |||
| 486 : | `tkrat' | ||
| 487 : | A graphical mail reader which supports most MIME types, written in | ||
| 488 : | tcl/tk. This program has a nice feel and allows you to create a | ||
| 489 : | searchable database of old mail messages, but has a hopeless | ||
| 490 : | locking mechanism. | ||
| 491 : | |||
| 492 : | |||
| 493 : | File: unix.info, Node: File transfer, Next: Compilers, Prev: Mail, Up: UNIX command overview | ||
| 494 : | |||
| 495 : | File transfer | ||
| 496 : | ------------- | ||
| 497 : | |||
| 498 : | `ftp' | ||
| 499 : | The File Transfer program - copies files to/from a remote host. | ||
| 500 : | |||
| 501 : | `ncftp' | ||
| 502 : | An enhanced ftp for anonymous login. | ||
| 503 : | |||
| 504 : | |||
| 505 : | File: unix.info, Node: Compilers, Next: Interpreted languages, Prev: File transfer, Up: UNIX command overview | ||
| 506 : | |||
| 507 : | Compilers | ||
| 508 : | --------- | ||
| 509 : | |||
| 510 : | `cc' | ||
| 511 : | The C compiler. | ||
| 512 : | |||
| 513 : | `CC' | ||
| 514 : | The C++ compiler. | ||
| 515 : | |||
| 516 : | `gcc' | ||
| 517 : | The GNU C compiler. | ||
| 518 : | |||
| 519 : | `g++' | ||
| 520 : | The GNU C++ compiler. | ||
| 521 : | |||
| 522 : | `ld' | ||
| 523 : | The system linker/loader. | ||
| 524 : | |||
| 525 : | `ar' | ||
| 526 : | Archive library builder. | ||
| 527 : | |||
| 528 : | `dbx' | ||
| 529 : | A symbolic debugger. | ||
| 530 : | |||
| 531 : | `gdb' | ||
| 532 : | The GNU symbolic debugger. | ||
| 533 : | |||
| 534 : | `xxgdb' | ||
| 535 : | The GNU debugger with a windown driven front-end. | ||
| 536 : | |||
| 537 : | `ddd' | ||
| 538 : | A motif based front-end to the gdb debugger. | ||
| 539 : | |||
| 540 : | |||
| 541 : | File: unix.info, Node: Interpreted languages, Next: System statistics, Prev: Compilers, Up: UNIX command overview | ||
| 542 : | |||
| 543 : | Other interpreted languages | ||
| 544 : | --------------------------- | ||
| 545 : | |||
| 546 : | `perl' | ||
| 547 : | Practical extraction an report language. | ||
| 548 : | |||
| 549 : | `tcl' | ||
| 550 : | A perl-like language with special support for building user | ||
| 551 : | interfaces and command shells. | ||
| 552 : | |||
| 553 : | `scheme' | ||
| 554 : | A lisp-like extensible scripting language from GNU. | ||
| 555 : | |||
| 556 : | `mercury' | ||
| 557 : | A prolog-like language for artificial intelligence. | ||
| 558 : | |||
| 559 : | |||
| 560 : | File: unix.info, Node: System statistics, Next: System identity, Prev: Interpreted languages, Up: UNIX command overview | ||
| 561 : | |||
| 562 : | Processes and system statistics | ||
| 563 : | ------------------------------- | ||
| 564 : | |||
| 565 : | `ps' | ||
| 566 : | List system process table. | ||
| 567 : | |||
| 568 : | `vmstat' | ||
| 569 : | List kernel virtual-memory statistics. | ||
| 570 : | |||
| 571 : | `netstat' | ||
| 572 : | List network connections and statistics. | ||
| 573 : | |||
| 574 : | `rpcinfo' | ||
| 575 : | Show rpc information. | ||
| 576 : | |||
| 577 : | `showmount' | ||
| 578 : | Show clients mounting local filesystems. | ||
| 579 : | |||
| 580 : | |||
| 581 : | File: unix.info, Node: System identity, Next: Internet resources, Prev: System statistics, Up: UNIX command overview | ||
| 582 : | |||
| 583 : | System identity | ||
| 584 : | --------------- | ||
| 585 : | |||
| 586 : | `uname' | ||
| 587 : | Display system name and operating system release. | ||
| 588 : | |||
| 589 : | `hostname' | ||
| 590 : | Show the name of this host. | ||
| 591 : | |||
| 592 : | `domainname' | ||
| 593 : | Show the name of the local NIS domain. Normally this is chosen to | ||
| 594 : | be the same as the BIND/DNS domain, but it need not be. | ||
| 595 : | |||
| 596 : | `nslookup' | ||
| 597 : | Interrogate the DNS/BIND name service (hostname to IP address | ||
| 598 : | conversion). | ||
| 599 : | |||
| 600 : | |||
| 601 : | File: unix.info, Node: Internet resources, Next: Text/postscript, Prev: System identity, Up: UNIX command overview | ||
| 602 : | |||
| 603 : | Internet resources | ||
| 604 : | ------------------ | ||
| 605 : | |||
| 606 : | `archie, xarchie' | ||
| 607 : | Search the internet ftp database for files. | ||
| 608 : | |||
| 609 : | `xrn, fnews' | ||
| 610 : | Read news (browser). | ||
| 611 : | |||
| 612 : | `netscape, xmosaic' | ||
| 613 : | Read world wide web (WWW) (browser). | ||
| 614 : | |||
| 615 : | |||
| 616 : | File: unix.info, Node: Text/postscript, Next: Pictures/graphics, Prev: Internet resources, Up: UNIX command overview | ||
| 617 : | |||
| 618 : | Text formatting and postscript | ||
| 619 : | ------------------------------ | ||
| 620 : | |||
| 621 : | `tex, latex' | ||
| 622 : | Donald Knuth's text formatting language, pronounced "tek" (the x | ||
| 623 : | is really a greek "chi"). Used widely for technical publications. | ||
| 624 : | Compiles to dvi (device independent) file format. | ||
| 625 : | |||
| 626 : | `texinfo' | ||
| 627 : | A hypertext documentation system using tex and "info" format. This | ||
| 628 : | is the GNU documentation system. This UNIX guide is written in | ||
| 629 : | texinfo!!! | ||
| 630 : | |||
| 631 : | `xdvi' | ||
| 632 : | View a tex dvi file on screen. | ||
| 633 : | |||
| 634 : | `dvips' | ||
| 635 : | Convert dvi format into postscript. | ||
| 636 : | |||
| 637 : | `ghostview, ghostscript' | ||
| 638 : | View a postscript file on screen. | ||
| 639 : | |||
| 640 : | |||
| 641 : | File: unix.info, Node: Pictures/graphics, Next: Miscellaneous, Prev: Text/postscript, Up: UNIX command overview | ||
| 642 : | |||
| 643 : | Picture editors and processors | ||
| 644 : | ------------------------------ | ||
| 645 : | |||
| 646 : | `xv' | ||
| 647 : | Handles, edits and processes pictures in a variety of standard | ||
| 648 : | graphics formats (gif, jpg, tiff etc). Use `xv -quit' to place a | ||
| 649 : | picture on your root window. | ||
| 650 : | |||
| 651 : | `xpaint' | ||
| 652 : | A simple paint program. | ||
| 653 : | |||
| 654 : | `xfig' | ||
| 655 : | A line drawing figure editor. Produces postscript, tex, and a | ||
| 656 : | variety of other output formats. | ||
| 657 : | |||
| 658 : | `xsetroot' | ||
| 659 : | Load an X-bitmap image into the screen (root window) background. | ||
| 660 : | Small images are tiled. | ||
| 661 : | |||
| 662 : | |||
| 663 : | File: unix.info, Node: Miscellaneous, Prev: Pictures/graphics, Up: UNIX command overview | ||
| 664 : | |||
| 665 : | Miscellaneous | ||
| 666 : | ------------- | ||
| 667 : | |||
| 668 : | `date' | ||
| 669 : | Print the date and time. | ||
| 670 : | |||
| 671 : | `ispell' | ||
| 672 : | Spelling checker. | ||
| 673 : | |||
| 674 : | `xcalc' | ||
| 675 : | A graphical calculator. | ||
| 676 : | |||
| 677 : | `dc,bc' | ||
| 678 : | Text-based calculators. | ||
| 679 : | |||
| 680 : | `xclock' | ||
| 681 : | A clock! | ||
| 682 : | |||
| 683 : | `ping' | ||
| 684 : | Send a "sonar" ping to see if another unix host is alive. | ||
| 685 : | |||
| 686 : | |||
| 687 : | File: unix.info, Node: Terminals, Next: The X window system, Prev: UNIX command overview, Up: The login environment | ||
| 688 : | |||
| 689 : | Terminals | ||
| 690 : | ========= | ||
| 691 : | |||
| 692 : | In order to communicate with a user, a shell needs to have access to | ||
| 693 : | a terminal. Unix was designed to work with many different kinds of | ||
| 694 : | terminals. Input/output commands in Unix read and write to a virtual | ||
| 695 : | terminal. In _reality_ a terminal might be a text-based Teletype | ||
| 696 : | terminal (called a _tty_ for short) or a graphics based terminal; it | ||
| 697 : | might be 80-characters wide or it might be wider or narrower. Unix take | ||
| 698 : | into account these possibility by defining a number of instances of | ||
| 699 : | terminals in a more or less object oriented way. | ||
| 700 : | |||
| 701 : | Each user's terminal has to be configured before cursor based | ||
| 702 : | input/output will work correctly. Normally this is done by choosing one | ||
| 703 : | of a number of standard terminal types a list which is supplied by the | ||
| 704 : | system. In practice the user defines the value of the environment | ||
| 705 : | variable `TERM' to an appropriate name. Typical examples are `vt100' | ||
| 706 : | and `xterm'. If no standard setup is found, the terminal can always be | ||
| 707 : | configured manually using UNIX's most cryptic and opaque of commands: | ||
| 708 : | `stty'. | ||
| 709 : | |||
| 710 : | The job of configuring terminals is much easier now that hardware is | ||
| 711 : | more standard. Users' terminals are usually configured centrally by the | ||
| 712 : | system administrator and it is seldom indeed that one ever has to | ||
| 713 : | choose anything other than `vt100' or `xterm'. | ||
| 714 : | |||
| 715 : | |||
| 716 : | File: unix.info, Node: The X window system, Next: Multiple screens, Prev: Terminals, Up: The login environment | ||
| 717 : | |||
| 718 : | The X window system | ||
| 719 : | =================== | ||
| 720 : | |||
| 721 : | Because UNIX originated before windowing technology was available, | ||
| 722 : | the user-interface was not designed with windowing in mind. The X window | ||
| 723 : | system attempts to be like a virtual machine park, running a different | ||
| 724 : | program in each window. Although the programs appear on one screen, they | ||
| 725 : | may in fact be running on unix systems anywhere in the world, with only | ||
| 726 : | the output being local to the user's display. The standard shell | ||
| 727 : | interface is available by running an X client application called | ||
| 728 : | `xterm' which is a graphical front-end to the standard UNIX textual | ||
| 729 : | interface. | ||
| 730 : | |||
| 731 : | The `xterm' program provides a virtual terminal using the X windows | ||
| 732 : | graphical user interface. It works in exactly the same way as a _tty_ | ||
| 733 : | terminal, except that standard graphical facilities like copy and paste | ||
| 734 : | are available. Moreover, the user has the convenience of being able to | ||
| 735 : | run a different shell in every window. For example, using the `rlogin' | ||
| 736 : | command, it is possible to work on the local system in one window, and | ||
| 737 : | on another remote system in another window. The X-window environment | ||
| 738 : | allows one to cut and paste between windows, regardless of which host | ||
| 739 : | the shell runs on. | ||
| 740 : | |||
| 741 : | * Menu: | ||
| 742 : | |||
| 743 : | * Components of X:: | ||
| 744 : | * How to set up X windows:: | ||
| 745 : | * X displays and authority:: | ||
| 746 : | |||
| 747 : | |||
| 748 : | File: unix.info, Node: Components of X, Next: How to set up X windows, Prev: The X window system, Up: The X window system | ||
| 749 : | |||
| 750 : | The components of the X-window system | ||
| 751 : | ------------------------------------- | ||
| 752 : | |||
| 753 : | The X11 system is based on the client-server model. You might wonder | ||
| 754 : | why a window system would be based on a model which was introduced for | ||
| 755 : | interprocess communication, or network communication. The answer is | ||
| 756 : | straightforward. | ||
| 757 : | |||
| 758 : | The designers of the X window system realized that network | ||
| 759 : | communication was to be the paradigm of the next generation of computer | ||
| 760 : | systems. They wanted to design a system of windows which would enable | ||
| 761 : | a user to sit at a terminal in Massachusetts and work on a machine in | ||
| 762 : | Tokyo - and still be able to get high quality windows displayed on | ||
| 763 : | their terminal. The aim of X windows from the beginning is to create a | ||
| 764 : | _distributed_ window environment. | ||
| 765 : | |||
| 766 : | When I log onto my friend's Hewlett Packard workstation to use the | ||
| 767 : | text editor (because I don't like the one on my EUNUCHS workstation) I | ||
| 768 : | want it to work correctly on my screen, with my keyboard - even though | ||
| 769 : | my workstation is manufactured by a different company. I also want the | ||
| 770 : | colours to be right despite the fact that the HP machine uses a | ||
| 771 : | completely different video hardware to my machine. When I press the | ||
| 772 : | curly brace key `{', I want to see a curly brace, and not some | ||
| 773 : | hieroglyphic because the HP station uses a different keyboard. | ||
| 774 : | |||
| 775 : | These are the problems which X tries to address. In a network | ||
| 776 : | environment we need a _common window system_ which will work on any | ||
| 777 : | kind of hardware, and hide the differences between different machines as | ||
| 778 : | far as possible. But it has to be flexible enough to allow us to change | ||
| 779 : | all of the things we don't like - to choose our own colours, and the | ||
| 780 : | kind of window borders we want etc. Other windowing systems (like | ||
| 781 : | Microsoft windows) ignore these problems and thereby lock the user to a | ||
| 782 : | single vendors products and a single operating system. (That, of course, | ||
| 783 : | is no accident.) | ||
| 784 : | |||
| 785 : | The way X solves this problem is to use the client server model. | ||
| 786 : | Each program which wants to open a window on somebody's compute screen | ||
| 787 : | is a client of the _X window service_. To get something drawn on a | ||
| 788 : | user's screen, the client asks a server on the host of interest to draw | ||
| 789 : | windows for it. No client ever draws anything itself - it asks the | ||
| 790 : | server to do it on its behalf. There are several reasons for this: | ||
| 791 : | |||
| 792 : | * The clients can all talk a common `window language' or _protocol_. | ||
| 793 : | We can hide the difference between different kinds of hardware by | ||
| 794 : | making the _machine-specific_ part of drawing graphics entirely a | ||
| 795 : | problem of implementing the server on the particular hardware. | ||
| 796 : | When a new type of hardware comes along, we just need to modify | ||
| 797 : | the server - none of the clients need to be modified. | ||
| 798 : | |||
| 799 : | * We can contact different servers and send our output to different | ||
| 800 : | hardware - thus even though a program is running on a CPU in Tokyo, | ||
| 801 : | it can ask the server in Massachusetts to display its window for | ||
| 802 : | it. | ||
| 803 : | |||
| 804 : | * When more than one window is on a user's display, it eventually | ||
| 805 : | becomes necessary to move the windows around and then figure out | ||
| 806 : | which windows are on top of which other windows etc. If all of the | ||
| 807 : | drawing information is kept in a server, it is straightforward to | ||
| 808 : | work out this information. If every client drew where it wanted to, | ||
| 809 : | it would be impossible to know which window was supposed to be on | ||
| 810 : | top of another. | ||
| 811 : | |||
| 812 : | In X, the window manager is a different program to the server which | ||
| 813 : | does the drawing of graphics - but the client-server idea still | ||
| 814 : | applies, it just has one more piece to its puzzle. | ||
| 815 : | |||
| 816 : | |||
| 817 : | File: unix.info, Node: How to set up X windows, Next: X displays and authority, Prev: Components of X, Up: The X window system | ||
| 818 : | |||
| 819 : | How to set up X windows | ||
| 820 : | ----------------------- | ||
| 821 : | |||
| 822 : | The X windows system is large and complex and not particularly user | ||
| 823 : | friendly. When you log in to the system, X reads two files in your home | ||
| 824 : | directory which decide which applications will be started what they will | ||
| 825 : | look like. The files are called | ||
| 826 : | |||
| 827 : | _.Xsession_ | ||
| 828 : | This file is a shell script which starts up a number of | ||
| 829 : | applications as background processes and exits by calling a window | ||
| 830 : | manager. Here is a simple example file | ||
| 831 : | |||
| 832 : | #!/bin/csh | ||
| 833 : | # | ||
| 834 : | # .xsession file | ||
| 835 : | # | ||
| 836 : | # | ||
| 837 : | |||
| 838 : | setenv PATH /usr/bin:/bin:/local/gnu/bin:/usr/X11R6/bin | ||
| 839 : | |||
| 840 : | # | ||
| 841 : | # List applications here, with & at the end | ||
| 842 : | # so they run in the background | ||
| 843 : | # | ||
| 844 : | |||
| 845 : | xterm -T NewTitle -sl 1000 -geometry 90x45+16+150 -sb & | ||
| 846 : | xclock & | ||
| 847 : | xbiff -geometry 80x80+510+0 & | ||
| 848 : | |||
| 849 : | # Start a window manager. Exec replaces this script with | ||
| 850 : | # the fvwm process, so that it doesn't exist as a separate | ||
| 851 : | # (useless) process. | ||
| 852 : | |||
| 853 : | exec /local/bin/fvwm | ||
| 854 : | |||
| 855 : | _.Xdefaults_ | ||
| 856 : | This file specifies all of the resources which X programs use. It | ||
| 857 : | can be used to change the colours used by applications, or font | ||
| 858 : | types etc. The subject of X-rescources is a large one and we don't | ||
| 859 : | have time for it here. Here is a simple example, which shows how | ||
| 860 : | you can make your over-bright xterm and emacs windows less bright | ||
| 861 : | grey shade. | ||
| 862 : | |||
| 863 : | xterm*background: LightGrey | ||
| 864 : | Emacs*background: grey92 | ||
| 865 : | Xemacs*background: grey92 | ||
| 866 : | |||
| 867 : | |||
| 868 : | File: unix.info, Node: X displays and authority, Prev: How to set up X windows, Up: The X window system | ||
| 869 : | |||
| 870 : | X displays and authority | ||
| 871 : | ------------------------ | ||
| 872 : | |||
| 873 : | In the terminology used by X11, every client program has to contact a | ||
| 874 : | _display_ in order to open a window. A display is a virtual screen | ||
| 875 : | which is created by the X server on a particular host. X can create | ||
| 876 : | several separate displays on a given host, though most machines only | ||
| 877 : | have one. | ||
| 878 : | |||
| 879 : | When an X client program wants to open a window, it looks in the UNIX | ||
| 880 : | environment variable `DISPLAY' for the IP address of a host which has | ||
| 881 : | an X server it can contact. For example, if we wrote | ||
| 882 : | setenv DISPLAY myhost:0 | ||
| 883 : | the client would try to contact the X server on `myhost' and ask for | ||
| 884 : | a window on display number zero (the usual display). If we wrote | ||
| 885 : | setenv DISPLAY 198.112.208.35:0 | ||
| 886 : | |||
| 887 : | the client would try to open display zero on the X server at the host | ||
| 888 : | with the IP address `198.112.208.35'. | ||
| 889 : | |||
| 890 : | Clearly there must be some kind of security mechanism to prevent just | ||
| 891 : | anybody from opening windows on someone's display. X has two such | ||
| 892 : | mechanisms: | ||
| 893 : | |||
| 894 : | _xhost_ | ||
| 895 : | This mechanism is now obsolete. The `xhost' command is used to | ||
| 896 : | define a list of hosts which are allowed to open windows on the | ||
| 897 : | user's display. It cannot destinguish between individual users. | ||
| 898 : | i.e. the command `xhost yourhost' would allow _anyone_ using | ||
| 899 : | yourhost to access the local display. This mechanism is only | ||
| 900 : | present for backward compatibility with early versions of X | ||
| 901 : | windows. Normally one should use the command `xhost -' to exclude | ||
| 902 : | all others from accessing the display. | ||
| 903 : | |||
| 904 : | _Xauthority_ | ||
| 905 : | The Xauthority mechanism has replaced the xhost scheme. It provides | ||
| 906 : | a security mechanism which can distinguish individual users, not | ||
| 907 : | just hosts. In order for a user to open a window on a display, | ||
| 908 : | he/she must have a ticket--called a "magic cookie". This is a | ||
| 909 : | binary file called `.Xauthority' which is created in the user's | ||
| 910 : | home directory when he/she first starts the X-windows system. | ||
| 911 : | Anyone who does not have a recent copy of this file cannot open | ||
| 912 : | windows or read the display of the user's terminal. This mechanism | ||
| 913 : | is based on the idea that the user's home directory is available | ||
| 914 : | via NFS on all hosts he/she will log onto, and thus the owner of | ||
| 915 : | the display will always have access to the magic cookie, and will | ||
| 916 : | therefore always be able to open windows on the display. Other | ||
| 917 : | users must obtain a copy of the file in order to open windows | ||
| 918 : | there. The command `xauth' is an interactive utility used for | ||
| 919 : | controlling the contents of the `.Xauthority' file. See the | ||
| 920 : | `xauth' manual page for more information. | ||
| 921 : | |||
| 922 : | |||
| 923 : | File: unix.info, Node: Multiple screens, Prev: The X window system, Up: The login environment | ||
| 924 : | |||
| 925 : | Multiple screens | ||
| 926 : | ================ | ||
| 927 : | |||
| 928 : | The window paradigm has been very successful in many ways, but anyone | ||
| 929 : | who has used a window system knows that the screen is simply not big | ||
| 930 : | enough for all the windows one would like! Unix has several solutions to | ||
| 931 : | this problem. | ||
| 932 : | |||
| 933 : | One solution is to attach several physical screens to a terminal. | ||
| 934 : | The X window system can support any number of physical screens of | ||
| 935 : | different types. A graphical designer might want a high resolution | ||
| 936 : | colour screen for drawing and a black and white screen for writing | ||
| 937 : | text, for instance. The disadvantage with this method is the cost of | ||
| 938 : | the hardware. | ||
| 939 : | |||
| 940 : | A cheaper solution is to use a window manager such as `fwvm' which | ||
| 941 : | creates a virtual screen of unlimited size on a single monitor. As the | ||
| 942 : | mouse pointer reaches the edge of the true screen, the window manager | ||
| 943 : | replaces the display with a new "blank screen" in which to place | ||
| 944 : | windows. A miniaturized image of the windows on a control panel acts as | ||
| 945 : | a map which makes it possible to find the applications on the virtual | ||
| 946 : | screen. | ||
| 947 : | |||
| 948 : | Yet another possibility is to create virtual displays inside a single | ||
| 949 : | window. In other words, one can collapse several shell windows into a | ||
| 950 : | single `xterm' window by running the program `screen'. The screen | ||
| 951 : | command allows you to start several shells in a single window (using | ||
| 952 : | <CTRL-a CTRL-c>) and to switch between them (by typing <CTRL-a | ||
| 953 : | CTRL-n>). It is only possible to see one shell window at a time, but it | ||
| 954 : | is still possible to cut and paste between windows and one has a | ||
| 955 : | considerable saving of space. The `screen' command also allows you to | ||
| 956 : | suspend a shell session, log out, log in again later and resume the | ||
| 957 : | session precisely where you left off. | ||
| 958 : | |||
| 959 : | Here is a summary of some useful screen commands: | ||
| 960 : | |||
| 961 : | `screen' | ||
| 962 : | Start the screen server. | ||
| 963 : | |||
| 964 : | `screen -r' | ||
| 965 : | Resume a previously suspended screen session if possible. | ||
| 966 : | |||
| 967 : | `CTRL-a CTRL-c' | ||
| 968 : | Start a new shell on top of the others (a fresh `screen') in the | ||
| 969 : | current window. | ||
| 970 : | |||
| 971 : | `CTRL-a CTRL-n' | ||
| 972 : | Switch to the next `screen'. | ||
| 973 : | |||
| 974 : | `CTRL-a CTRL-a' | ||
| 975 : | Switch to the last screen used. | ||
| 976 : | |||
| 977 : | `CTRL-a a' | ||
| 978 : | When screen is running, `CTRL-a' is used for screen commands and | ||
| 979 : | cannot therefore be used in its usual shell meaning of `jump to | ||
| 980 : | start of line'. `CTRL-a a' replaces this. | ||
| 981 : | |||
| 982 : | `CTRL-a CTRL-d' | ||
| 983 : | Detach the screen session from the current window so that it can | ||
| 984 : | be resumed later. It can be resumed with the `screen -r' command. | ||
| 985 : | |||
| 986 : | `CTRL-a ?' | ||
| 987 : | Help screen. | ||
| 988 : | |||
| 989 : | |||
| 990 : | File: unix.info, Node: Files and access, Next: C shell, Prev: The login environment, Up: Top | ||
| 991 : | |||
| 992 : | Files and access | ||
| 993 : | **************** | ||
| 994 : | |||
| 995 : | To prevent all users from being able to access all files on the | ||
| 996 : | system, unix records information about _who_ creates files and also who | ||
| 997 : | is allowed to access them later. | ||
| 998 : | |||
| 999 : | Each user has a unique _username_ or _loginname_ together with a | ||
| 1000 : | unique _user id_ or _uid_. The user id is a number, whereas the login | ||
| 1001 : | name is a text string - otherwise the two express the same information. | ||
| 1002 : | A file belongs to user A if it is _owned_ by user A. User A then | ||
| 1003 : | decides whether or not other users can read, write or execute the file | ||
| 1004 : | by setting the _protection bits_ or the _permission_ of the file using | ||
| 1005 : | the command `chmod'. | ||
| 1006 : | |||
| 1007 : | In addition to user identities, there are groups of users. The idea | ||
| 1008 : | of a group is that several named users might want to be able to read | ||
| 1009 : | and work on a file, without other users being able to access it. Every | ||
| 1010 : | user is a member of at least one group, called the _login group_ and | ||
| 1011 : | each group has both a textual name and a number (_group id_). The | ||
| 1012 : | _uid_ and _gid_ of each user is recorded in the file `/etc/passwd' (See | ||
| 1013 : | chapter 6). Membership of other groups is recorded in the file | ||
| 1014 : | `/etc/group' or on some systems `/etc/logingroup'. | ||
| 1015 : | |||
| 1016 : | * Menu: | ||
| 1017 : | |||
| 1018 : | * Protection bits:: | ||
| 1019 : | * chmod:: | ||
| 1020 : | * Umask:: | ||
| 1021 : | * s-bit and t-bit:: | ||
| 1022 : | |||
| 1023 : | |||
| 1024 : | File: unix.info, Node: Protection bits, Next: chmod, Prev: Files and access, Up: Files and access | ||
| 1025 : | |||
| 1026 : | Protection bits | ||
| 1027 : | =============== | ||
| 1028 : | |||
| 1029 : | The following output is from the command `ls -lag' executed on a | ||
| 1030 : | SunOS type machine. | ||
| 1031 : | |||
| 1032 : | lrwxrwxrwx 1 root wheel 7 Jun 1 1993 bin -> usr/bin | ||
| 1033 : | -r--r--r-- 1 root bin 103512 Jun 1 1993 boot | ||
| 1034 : | drwxr-sr-x 2 bin staff 11264 May 11 17:00 dev | ||
| 1035 : | drwxr-sr-x 10 bin staff 2560 Jul 8 02:06 etc | ||
| 1036 : | drwxr-sr-x 8 root wheel 512 Jun 1 1993 export | ||
| 1037 : | drwx------ 2 root daemon 512 Sep 26 1993 home | ||
| 1038 : | -rwxr-xr-x 1 root wheel 249079 Jun 1 1993 kadb | ||
| 1039 : | lrwxrwxrwx 1 root wheel 7 Jun 1 1993 lib -> usr/lib | ||
| 1040 : | drwxr-xr-x 2 root wheel 8192 Jun 1 1993 lost+found | ||
| 1041 : | drwxr-sr-x 2 bin staff 512 Jul 23 1992 mnt | ||
| 1042 : | dr-xr-xr-x 1 root wheel 512 May 11 17:00 net | ||
| 1043 : | drwxr-sr-x 2 root wheel 512 Jun 1 1993 pcfs | ||
| 1044 : | drwxr-sr-x 2 bin staff 512 Jun 1 1993 sbin | ||
| 1045 : | lrwxrwxrwx 1 root wheel 13 Jun 1 1993 sys->kvm/sys | ||
| 1046 : | drwxrwxrwx 6 root wheel 732 Jul 8 19:23 tmp | ||
| 1047 : | drwxr-xr-x 27 root wheel 1024 Jun 14 1993 usr | ||
| 1048 : | drwxr-sr-x 10 bin staff 512 Jul 23 1992 var | ||
| 1049 : | -rwxr-xr-x 1 root daemon 2182656 Jun 4 1993 vmunix | ||
| 1050 : | The first column is a textual representation of the protection bits | ||
| 1051 : | for each file. Column two is the number of hard links to the file (See | ||
| 1052 : | exercises below). The third and fourth columns are the user name and | ||
| 1053 : | group name and the remainder show the file size in bytes and the | ||
| 1054 : | creation date. Notice that the directories `/bin' and `/sys' are | ||
| 1055 : | symbolic links to other directories. | ||
| 1056 : | |||
| 1057 : | There are sixteen protection bits for a UNIX file, but only twelve | ||
| 1058 : | of them can be changed by users. These twelve are split into four groups | ||
| 1059 : | of three. Each three-bit number corresponds to one _octal_ number. | ||
| 1060 : | |||
| 1061 : | The leading four invisible bits gives information about the type of | ||
| 1062 : | file: is the file a _plain file_, a _directory_ or a _link_. In the | ||
| 1063 : | output from `ls' this is represented by a single character: `-', `d' or | ||
| 1064 : | `l'. | ||
| 1065 : | |||
| 1066 : | The next three bits set the so-called _s-bits_ and _t-bit_ which are | ||
| 1067 : | explained below. | ||
| 1068 : | |||
| 1069 : | The remaining three groups of three bits set flags which indicate | ||
| 1070 : | whether a file can be read `r', written to `w' or executed `x' by (i) | ||
| 1071 : | the user who created them, (ii) the other users who are in the group | ||
| 1072 : | the file is marked with, and (iii) any user at all. | ||
| 1073 : | |||
| 1074 : | For example, the permission | ||
| 1075 : | |||
| 1076 : | Type Owner Group Anyone | ||
| 1077 : | d rwx r-x --- | ||
| 1078 : | |||
| 1079 : | tells us that the file is a directory, which can be read and written to | ||
| 1080 : | by the owner, can be read by others in its group, but not by anyone | ||
| 1081 : | else. | ||
| 1082 : | |||
| 1083 : | _Note about directories. It is impossible to `cd' to a directory | ||
| 1084 : | unless the `x' bit is set. That is, directories must be `executable' in | ||
| 1085 : | order to be accessible._ | ||
| 1086 : | |||
| 1087 : | Here are some examples of the relationship between binary, octal and | ||
| 1088 : | the textual representation of file modes. | ||
| 1089 : | |||
| 1090 : | Binary Octal Text | ||
| 1091 : | |||
| 1092 : | 001 1 x | ||
| 1093 : | 010 2 w | ||
| 1094 : | 100 4 r | ||
| 1095 : | 110 6 rw- | ||
| 1096 : | 101 5 r-x | ||
| 1097 : | - 644 rw-r--r-- | ||
| 1098 : | |||
| 1099 : | It is well worth becoming familiar with the octal number representation | ||
| 1100 : | of these permissions. | ||
| 1101 : | |||
| 1102 : | |||
| 1103 : | File: unix.info, Node: chmod, Next: Umask, Prev: Protection bits, Up: Files and access | ||
| 1104 : | |||
| 1105 : | chmod | ||
| 1106 : | ===== | ||
| 1107 : | |||
| 1108 : | The `chmod' command changes the permission or _mode_ of a file. Only | ||
| 1109 : | the owner of the file or the superuser can change the permission. Here | ||
| 1110 : | are some examples of its use. Try them. | ||
| 1111 : | |||
| 1112 : | # make read/write-able for everyone | ||
| 1113 : | chmod a+w myfile | ||
| 1114 : | |||
| 1115 : | # add the 'execute' flag for directory | ||
| 1116 : | chmod u+x mydir/ | ||
| 1117 : | |||
| 1118 : | # open all files for everyone | ||
| 1119 : | chmod 755 * | ||
| 1120 : | |||
| 1121 : | # set the s-bit on my-dir's group | ||
| 1122 : | chmod g+s mydir/ | ||
| 1123 : | |||
| 1124 : | # descend recursively into directory opening all files | ||
| 1125 : | chmod -R a+r dir | ||
| 1126 : | |||
| 1127 : | |||
| 1128 : | File: unix.info, Node: Umask, Next: s-bit and t-bit, Prev: chmod, Up: Files and access | ||
| 1129 : | |||
| 1130 : | Umask | ||
| 1131 : | ===== | ||
| 1132 : | |||
| 1133 : | When a new file gets created, the operating system must decide what | ||
| 1134 : | default protection bits to set on that file. The variable `umask' | ||
| 1135 : | decides this. `umask' is normally set by each user in his or her | ||
| 1136 : | `.cshrc' file (see next chapter). For example | ||
| 1137 : | umask 077 # safe | ||
| 1138 : | umask 022 # liberal | ||
| 1139 : | |||
| 1140 : | According the UNIX documentation, the value of `umask' is `XOR'ed | ||
| 1141 : | (exclusive `OR') with a value of `666 & umask' for plain files or `777 | ||
| 1142 : | & umask' for directories in order to find out the standard protection. | ||
| 1143 : | Actually this is not quite true: `umask' only removes bits, it never | ||
| 1144 : | sets bits which were not already set in `666'. For instance | ||
| 1145 : | |||
| 1146 : | umask Permission | ||
| 1147 : | |||
| 1148 : | 077 600 (plain) | ||
| 1149 : | 077 700 (dir) | ||
| 1150 : | 022 644 (plain) | ||
| 1151 : | 022 755 (dir) | ||
| 1152 : | The correct rule for computing permissions is not XOR but `NOT AND'. | ||
| 1153 : | |||
| 1154 : | * Menu: | ||
| 1155 : | |||
| 1156 : | * Making programs executable:: | ||
| 1157 : | * chown and chgrp:: | ||
| 1158 : | * Making a group:: | ||
| 1159 : | |||
| 1160 : | |||
| 1161 : | File: unix.info, Node: Making programs executable, Next: chown and chgrp, Prev: Umask, Up: Umask | ||
| 1162 : | |||
| 1163 : | Making programs executable | ||
| 1164 : | -------------------------- | ||
| 1165 : | |||
| 1166 : | A unix program is normally executed by typing its pathname. If the | ||
| 1167 : | `x' execute bit is not set on the file, this will generate a | ||
| 1168 : | `Permission denied' error. This protects the system from interpreting | ||
| 1169 : | nonsense files as programs. To make a program executable for someone, | ||
| 1170 : | you must therefore ensure that they can execute the file, using a | ||
| 1171 : | command like | ||
| 1172 : | |||
| 1173 : | chmod u+x FILENAME | ||
| 1174 : | |||
| 1175 : | This command would set execute permissions for the owner of the file; | ||
| 1176 : | chmod ug+x FILENAME | ||
| 1177 : | |||
| 1178 : | would set execute permissions for the owner and for any users in the | ||
| 1179 : | same group as the file. Note that script programs must also be readable | ||
| 1180 : | in order to be executable, since the shell has the interpret them by | ||
| 1181 : | reading. | ||
| 1182 : | |||
| 1183 : | |||
| 1184 : | File: unix.info, Node: chown and chgrp, Next: Making a group, Prev: Making programs executable, Up: Umask | ||
| 1185 : | |||
| 1186 : | chown and chgrp | ||
| 1187 : | --------------- | ||
| 1188 : | |||
| 1189 : | These two commands change the ownership and the group ownership of a | ||
| 1190 : | file. Only the superuser can change the ownership of a file on most | ||
| 1191 : | systems. This is to prevent users from being able to defeat quota | ||
| 1192 : | mechanisms. (On some systems, which do not implement quotas, ordinary | ||
| 1193 : | users can give a file away to another user but not get it back again.) | ||
| 1194 : | The same applies to group ownership. | ||
| 1195 : | |||
| 1196 : | |||
| 1197 : | File: unix.info, Node: Making a group, Prev: chown and chgrp, Up: Umask | ||
| 1198 : | |||
| 1199 : | Making a group | ||
| 1200 : | -------------- | ||
| 1201 : | |||
| 1202 : | Normally users other than root cannot define their own groups. This | ||
| 1203 : | is a weakness in Unix from older times which no one seems to be in a | ||
| 1204 : | hurry to change. At Oslo College, Computer Science, we use a local | ||
| 1205 : | solution whereby users can edit a file to create their own groups. This | ||
| 1206 : | file is called `/iu/nexus/local/iu/etc/iu-group'. The format of the | ||
| 1207 : | group file is: | ||
| 1208 : | |||
| 1209 : | GROUP-NAME::GROUP-NUMBER:COMMA-SEPARATED-LIST-OF-USERS | ||
| 1210 : | |||
| 1211 : | |||
| 1212 : | File: unix.info, Node: s-bit and t-bit, Prev: Umask, Up: Files and access | ||
| 1213 : | |||
| 1214 : | s-bit and t-bit (sticky bit) | ||
| 1215 : | ============================ | ||
| 1216 : | |||
| 1217 : | The `s' and `t' bits have special uses. They are described as | ||
| 1218 : | follows. | ||
| 1219 : | |||
| 1220 : | Octal Text Name | ||
| 1221 : | |||
| 1222 : | 4000 chmod u+s Setuid bit | ||
| 1223 : | 2000 chmod g+s Setgid bit | ||
| 1224 : | 1000 chmod +t Sticky bit | ||
| 1225 : | |||
| 1226 : | The effect of these bits differs for plain files and directories and | ||
| 1227 : | differ between different versions of UNIX. You should check the manual | ||
| 1228 : | page `man sticky' to find out about your system! The following is | ||
| 1229 : | common behaviour. | ||
| 1230 : | |||
| 1231 : | For executable files, the setuid bit tells UNIX that _regardless of | ||
| 1232 : | who runs the program_ it should be executed with the permissions and | ||
| 1233 : | rights of owner of the file. This is often used to allow normal users | ||
| 1234 : | limited access to `root' privileges. A _setuid-root_ program is | ||
| 1235 : | executed as `root' for any user. The setgid bit sets the group | ||
| 1236 : | execution rights of the program in a similar way. | ||
| 1237 : | |||
| 1238 : | In BSD unix, if the setgid bit is set on a directory then any new | ||
| 1239 : | files created in that directory assume the group ownership of the | ||
| 1240 : | parent directory and not the logingroup of the user who created the | ||
| 1241 : | file. This is standard policy under system 5. | ||
| 1242 : | |||
| 1243 : | A directory for which the sticky bit is set restrict the deletion of | ||
| 1244 : | files within it. A file or directory inside a directory with the t-bit | ||
| 1245 : | set can only be deleted or renamed by its owner or the superuser. This | ||
| 1246 : | is useful for directories like the mail spool area and `/tmp' which | ||
| 1247 : | must be writable to everyone, but should not allow a user to delete | ||
| 1248 : | another user's files. | ||
| 1249 : | |||
| 1250 : | (Ultrix) If an executable file is marked with a sticky bit, it is | ||
| 1251 : | held in the memory or system swap area. It does not have to be fetched | ||
| 1252 : | from disk each time it is executed. This saves time for frequently used | ||
| 1253 : | programs like `ls'. | ||
| 1254 : | |||
| 1255 : | (Solaris 1) If a non-executable file is marked with the sticky bit, | ||
| 1256 : | it will _not_ be held in the disk page cache - that is, it is never | ||
| 1257 : | copied from the disk and held in RAM but is written to directly. This | ||
| 1258 : | is used to prevent certain files from using up valuable memory. | ||
| 1259 : | |||
| 1260 : | On some systems (e.g. ULTRIX), only the superuser can set the sticky | ||
| 1261 : | bit. On others (e.g. SunOS) any user can create a sticky directory. | ||
| 1262 : | |||
| 1263 : | |||
| 1264 : | File: unix.info, Node: C shell, Next: Bourne shell, Prev: Files and access, Up: Top | ||
| 1265 : | |||
| 1266 : | C shell | ||
| 1267 : | ******* | ||
| 1268 : | |||
| 1269 : | The C shell is the command interpreter which you use to run programs | ||
| 1270 : | and utilities. It contains a simple programming language for writing | ||
| 1271 : | tailor-made commands, and allows you to join together unix commands | ||
| 1272 : | with pipes. It is a configurable environment, and once you know it well, | ||
| 1273 : | it is the most efficient way of working with unix. | ||
| 1274 : | |||
| 1275 : | * Menu: | ||
| 1276 : | |||
| 1277 : | * .cshrc and .login:: | ||
| 1278 : | * Defining variables with set and setenv:: | ||
| 1279 : | * Arrays:: | ||
| 1280 : | * Pipes and redirection:: | ||
| 1281 : | * tee and script:: | ||
| 1282 : | * Command history:: | ||
| 1283 : | * Command/filename completion:: | ||
| 1284 : | * Single and double quotes:: | ||
| 1285 : | * Job control:: | ||
| 1286 : | * Scripts with argumemts:: | ||
| 1287 : | * subshells:: | ||
| 1288 : | * Tests and conditions:: | ||
| 1289 : | * Loops in csh:: | ||
| 1290 : | * Input from the user:: | ||
| 1291 : | * Extracting parts of a pathname:: | ||
| 1292 : | * Arithmetic:: | ||
| 1293 : | * Examples:: | ||
| 1294 : | |||
| 1295 : | |||
| 1296 : | File: unix.info, Node: .cshrc and .login, Next: Defining variables with set and setenv, Prev: C shell, Up: C shell | ||
| 1297 : | |||
| 1298 : | .cshrc and .login files | ||
| 1299 : | ======================= | ||
| 1300 : | |||
| 1301 : | Most users run the C-shell `/bin/csh' as their login environment, or | ||
| 1302 : | these days, preferably the `tcsh' which is an improved version of csh. | ||
| 1303 : | When a user logs in to a UNIX system the C-shell starts by reading some | ||
| 1304 : | files which configure the environment by defining variables like `path'. | ||
| 1305 : | |||
| 1306 : | * The file `.cshrc' is searched for in your home directory. i.e. | ||
| 1307 : | `~/.cshrc'. If it is found, its contents are interpreted by the | ||
| 1308 : | C-shell as C-shell instructions, before giving you the command | ||
| 1309 : | prompt(1). | ||
| 1310 : | |||
| 1311 : | * If and only if this is the _login shell_ (not a sub-shell that you | ||
| 1312 : | have started after login) then the file `~/.login' is searched for | ||
| 1313 : | and executed. | ||
| 1314 : | |||
| 1315 : | With the advent of the X11 windowing system, this has changed slightly. | ||
| 1316 : | Since the window system takes over the entire login procedure, users | ||
| 1317 : | never get to run `login shells', since the login shell is used up by | ||
| 1318 : | the X11 system. On an X-terminal or host running X the `.login' file | ||
| 1319 : | normally has no effect. | ||
| 1320 : | |||
| 1321 : | With some thought, the `.login' file can be eliminated entirely, and | ||
| 1322 : | we can put everything into the `.cshrc' file. Here is a very simple | ||
| 1323 : | example `.cshrc' file. | ||
| 1324 : | |||
| 1325 : | # | ||
| 1326 : | # .cshrc - read in by every csh that starts. | ||
| 1327 : | # | ||
| 1328 : | |||
| 1329 : | # Set the default file creation mask | ||
| 1330 : | umask 077 | ||
| 1331 : | |||
| 1332 : | # Set the path | ||
| 1333 : | set path=( /usr/local/bin /usr/bin/X11 /usr/ucb /bin /usr/bin . ) | ||
| 1334 : | |||
| 1335 : | # Exit here if the shell is not interactive | ||
| 1336 : | if ( $?prompt == 0 ) exit | ||
| 1337 : | |||
| 1338 : | # Set some variables | ||
| 1339 : | |||
| 1340 : | set noclobber notify filec nobeep | ||
| 1341 : | set history=100 | ||
| 1342 : | set prompt="`hostname`%" | ||
| 1343 : | set prompt2 = "%m %h>" # tcsh, prompt for foreach and while | ||
| 1344 : | |||
| 1345 : | setenv PRINTER myprinter | ||
| 1346 : | setenv LD_LIBRARY_PATH /usr/lib:/usr/local/lib:/usr/openwin/lib | ||
| 1347 : | |||
| 1348 : | # Aliases are shortcuts to unix commands | ||
| 1349 : | |||
| 1350 : | alias passwd yppasswd | ||
| 1351 : | alias dir 'ls -lg \!* | more' | ||
| 1352 : | alias sys 'ps aux | more' | ||
| 1353 : | alias h history | ||
| 1354 : | |||
| 1355 : | It is possible to make a much more complicated .cshrc file than this. | ||
| 1356 : | The advent of distributed computing and NFS (Network file system) means | ||
| 1357 : | that you might log into many different machines running different | ||
| 1358 : | versions of unix. The command path would have to be set differently for | ||
| 1359 : | each type of machine. | ||
| 1360 : | |||
| 1361 : | ---------- Footnotes ---------- | ||
| 1362 : | |||
| 1363 : | (1) Under HPUX, two other files are also read by the C-shell. These | ||
| 1364 : | are called `/etc/csh.login' and `/etc/src.csh', enabling some standard | ||
| 1365 : | set-up to be configured globally. GNU/Linux has a similar system. On | ||
| 1366 : | solaris systems `/etc/.login' is read. | ||
| 1367 : | |||
| 1368 : | |||
| 1369 : | File: unix.info, Node: Defining variables with set and setenv, Next: Arrays, Prev: .cshrc and .login, Up: C shell | ||
| 1370 : | |||
| 1371 : | Defining variables with set, setenv | ||
| 1372 : | =================================== | ||
| 1373 : | |||
| 1374 : | We have already seen in the examples above how to define variables in | ||
| 1375 : | C-shell. Let's formalize this. To define a local variable - that is, | ||
| 1376 : | one which will not get passed on to programs and sub-shells running | ||
| 1377 : | under the current shell, we write | ||
| 1378 : | |||
| 1379 : | set local = "some string" | ||
| 1380 : | set myname = "`whoami`" | ||
| 1381 : | |||
| 1382 : | These variables are then referred to by using the dollar `$' symbol. | ||
| 1383 : | i.e. The value of the variable `local' is `$local'. | ||
| 1384 : | |||
| 1385 : | echo $local $myname | ||
| 1386 : | |||
| 1387 : | Global variables, that is variables which all sub-shells inherit from | ||
| 1388 : | the current shell are defined using `setenv' | ||
| 1389 : | |||
| 1390 : | setenv GLOBAL "Some other string" | ||
| 1391 : | setenv MYNAME "`who am i`" | ||
| 1392 : | |||
| 1393 : | Their values are also referred to using the `$' symbol. Notice that | ||
| 1394 : | `set' uses an `=' sign while `setenv' does not. | ||
| 1395 : | |||
| 1396 : | Variables can be also created without a value. The shell uses this | ||
| 1397 : | method to switch on and off certain features, using variables like | ||
| 1398 : | `noclobber' and `noglob'. For instance | ||
| 1399 : | nexus% set flag | ||
| 1400 : | nexus% if ($?flag) echo 'Flag is set!' | ||
| 1401 : | Flag is set! | ||
| 1402 : | nexus% unset flag | ||
| 1403 : | nexus% if ( $?flag ) echo 'Flag is set!' | ||
| 1404 : | nexus% | ||
| 1405 : | |||
| 1406 : | The operator `$?VARIABLE' is `true' if VARIABLE exists and `false' if | ||
| 1407 : | it does not. It does not matter whether the variable holds any | ||
| 1408 : | information. | ||
| 1409 : | |||
| 1410 : | The commands `unset' and `unsetenv' can be used to undefine or | ||
| 1411 : | delete variables when you don't want them anymore. | ||
| 1412 : | |||
| 1413 : | |||
| 1414 : | File: unix.info, Node: Arrays, Next: Pipes and redirection, Prev: Defining variables with set and setenv, Up: C shell | ||
| 1415 : | |||
| 1416 : | Arrays | ||
| 1417 : | ====== | ||
| 1418 : | |||
| 1419 : | A useful facility in the C-shell is the ability to make arrays out of | ||
| 1420 : | strings and other variables. The round parentheses `(..)' do this. For | ||
| 1421 : | example, look at the following commands. | ||
| 1422 : | nexus% set array = ( a b c d ) | ||
| 1423 : | nexus% echo $array[1] | ||
| 1424 : | a | ||
| 1425 : | nexus% echo $array[2] | ||
| 1426 : | b | ||
| 1427 : | nexus% echo $array[$#array] | ||
| 1428 : | d | ||
| 1429 : | |||
| 1430 : | nexus% set noarray = ( "a b c d" ) | ||
| 1431 : | nexus% echo $noarray[1] | ||
| 1432 : | a b c d | ||
| 1433 : | nexus% echo $noarray[$#noarray] | ||
| 1434 : | a b c d | ||
| 1435 : | |||
| 1436 : | The first command defines an array containing the elements `a b c d'. | ||
| 1437 : | The elements of the array are referred to using square brackets `[..]' | ||
| 1438 : | and the first element is `$array[1]'. The last element is `$array[4]'. | ||
| 1439 : | _NOTE: this is not the same as in C or C++ where the first element of | ||
| 1440 : | the array is the zeroth element!_ | ||
| 1441 : | |||
| 1442 : | The special operator `$#' returns the number of elements in an array. | ||
| 1443 : | This gives us a simple way of finding the end of the array. For example | ||
| 1444 : | nexus% echo $#path | ||
| 1445 : | 23 | ||
| 1446 : | |||
| 1447 : | nexus% echo "The last element in path is $path[$#path]" | ||
| 1448 : | The last element in path is . | ||
| 1449 : | |||
| 1450 : | To find the next last element we need to be able to do arithmetic. We'll | ||
| 1451 : | come back to this later. | ||
| 1452 : |
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