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1.1 ! root 1: .\" Copyright (c) 1990 Regents of the University of California. ! 2: .\" All rights reserved. The Berkeley software License Agreement ! 3: .\" specifies the terms and conditions for redistribution. ! 4: .\" ! 5: .\" @(#)sh.1 6.6 (Berkeley) 7/24/90 ! 6: .\" ! 7: .Dd July 24, 1990 ! 8: .Dt SH 1 ! 9: .Os ATT 7th ! 10: .Sh NAME ! 11: .Nm sh ! 12: .Nd shell command interpreter ! 13: .Sh SYNOPSIS ! 14: .Nm sh ! 15: .Op Fl ceiknrstuvx ! 16: .Op arg ! 17: .Ar ... ! 18: .Sh DESCRIPTION ! 19: .Nm Sh ! 20: is a command programming language that executes commands read from a terminal ! 21: or a file. The shell this page describes is called the ! 22: .Em Bourne ! 23: shell. ! 24: .Pp ! 25: Command line options: ! 26: .Pp ! 27: If the first character of argument 0 if ! 28: .Fl , ! 29: commands are read from ! 30: .Pa $HOME/.profile , ! 31: if such a file exists. ! 32: The following flags are interpreted by the shell when it is invoked. ! 33: .Tw Fl ! 34: .Tp Cx Fl c ! 35: .Cx \&\ \& ! 36: .Ar string ! 37: .Cx ! 38: Commands are read from ! 39: .Ar string. ! 40: .Tp Fl s ! 41: If the ! 42: .Fl s ! 43: flag is present or if no arguments remain ! 44: then commands are read from the standard input. ! 45: Shell output is written to file descriptor 2. ! 46: .Tp Fl i ! 47: If the ! 48: .Fl i ! 49: flag is present or ! 50: if the shell input and output are attached to a terminal (as told by ! 51: .Xr getty ) ! 52: then this shell is ! 53: .Em interactive . ! 54: In this case the terminate signal SIGTERM (see ! 55: .Xr sigvec 2 ) ! 56: is ignored (so that 'kill 0' ! 57: does not kill an interactive shell) and the interrupt signal ! 58: SIGINT is caught and ignored (so that ! 59: .Xr wait ! 60: is interruptible). ! 61: In all cases SIGQUIT is ignored by the shell. ! 62: .Tp ! 63: .Pp ! 64: This next set of options can be used on the command line invoking ! 65: the ! 66: .Nm sh ! 67: or set with the interactive command ! 68: .Ic set . ! 69: .Tp Fl e ! 70: If non interactive, exit immediately if a command fails. ! 71: .Tp Fl k ! 72: All keyword arguments are placed in the environment for a command, ! 73: not just those that precede the command name. ! 74: .Tp Fl n ! 75: Read commands but do not execute them. ! 76: .Tp Fl t ! 77: Exit after reading and executing one command. ! 78: .Tp Fl u ! 79: Treat unset variables as an error when substituting. ! 80: .Tp Fl v ! 81: Print shell input lines as they are read. ! 82: .Tp Fl x ! 83: Print commands and their arguments as they are executed. ! 84: .Tp Fl ! 85: Turn off the ! 86: .Fl x ! 87: and ! 88: .Fl v ! 89: options. ! 90: .Tp ! 91: .Ss Commands . ! 92: A ! 93: .Em simple-command ! 94: is a sequence of non blank ! 95: .Em words ! 96: separated by blanks (a blank is a ! 97: .Em tab ! 98: or a ! 99: .Em space ) . ! 100: The first word specifies the name of the command to be executed. ! 101: Except as specified below the remaining words are passed as arguments ! 102: to the invoked command. ! 103: The command name is passed as argument 0 (see ! 104: .Xr execve 2 ) . ! 105: The ! 106: .Em value ! 107: of a simple-command is its exit status ! 108: if it terminates normally or ! 109: .Cx Li 200+ ! 110: .Em status ! 111: .Cx ! 112: if it terminates abnormally (see ! 113: .Ar sigvec 2 ! 114: for a list of status values). ! 115: .Pp ! 116: A ! 117: .Em pipeline ! 118: is a sequence of one or more ! 119: .Em commands ! 120: separated by ! 121: .Sq Nm \&| . ! 122: The standard output of each command but the last is connected by a ! 123: .Xr pipe 2 ! 124: to the standard input of the next command. ! 125: Each command is run as a separate process; ! 126: the shell waits for the last command to terminate. ! 127: .Pp ! 128: A ! 129: .Em list ! 130: is a sequence of one or more ! 131: .Em pipelines ! 132: separated by ! 133: .Nm \&; , ! 134: .Nm \&& , ! 135: .Nm \&&& ! 136: or ! 137: .Nm \&| ! 138: or ! 139: .Nm \&|\&| ! 140: and optionally terminated by ! 141: .Nm \&; ! 142: or ! 143: .Nm \&& . ! 144: .Nm \&; ! 145: and ! 146: .Nm \&& ! 147: have equal precedence which is lower than that of ! 148: .Nm \&&& ! 149: and ! 150: .Nm \&|\&| , ! 151: .Nm && ! 152: and ! 153: .Nm \&|\&| , ! 154: also have equal precedence. ! 155: A semicolon causes sequential execution; an ampersand causes the preceding ! 156: .Em pipeline ! 157: to be executed without waiting for it to finish. The symbol ! 158: .Nm \&&& ! 159: .Pq Nm \&|\&| ! 160: causes the ! 161: .Em list ! 162: following to be executed only if the preceding ! 163: .Em pipeline ! 164: returns a zero (non zero) value. Newlines may appear in a ! 165: .Em list , ! 166: instead of semicolons, to delimit commands. ! 167: .Pp ! 168: A ! 169: .Em command ! 170: is either a simple-command or one of the following. ! 171: The value returned by a command is that of the ! 172: last simple-command executed in the command. ! 173: .Tw Fl ! 174: .Tp Cx Ic for ! 175: .Cx \&\ \& ! 176: .Ar name ! 177: .Cx \&\ \& ! 178: .Op Ic in Ar word ... ! 179: .Cx \&\ \& ! 180: .Ic do ! 181: .Cx \&\ \& ! 182: .Ar list ! 183: .Cx \&\ \& ! 184: .Ic done ! 185: .Cx ! 186: Each time a ! 187: .Ic for ! 188: command is executed ! 189: .Ar name ! 190: is set to the next word in the ! 191: .Ic for ! 192: word list. ! 193: If ! 194: .Ic in ! 195: .Ar word \&... ! 196: is omitted, ! 197: .Ic in ! 198: .Dq Ic \&$@ ! 199: is assumed. Execution ends when there are no more words in the list. ! 200: .Tp Cx Ic case ! 201: .Cx \&\ \& ! 202: .Ar word ! 203: .Cx \&\ \& ! 204: .Ic in ! 205: .Cx \&\ \&[ ! 206: .Ar pattern ! 207: .Cx \&\ \& ! 208: .Op Ar \&| pattern ... ! 209: .Cx \&\ \& ! 210: .Ic \&) ! 211: .Cx \&\ \& ! 212: .Ar list ! 213: .Cx \&\ \& ! 214: .Ic \&;; ! 215: .Cx \&]\ \& ... ! 216: .Ar esac ! 217: .Cx ! 218: A ! 219: .Ic case ! 220: command executes the ! 221: .Ar list ! 222: associated with the first pattern that matches ! 223: .Ar word . ! 224: The form of the patterns is the same as that used for file name generation. ! 225: .Tp Cx Ic if ! 226: .Cx \&\ \& ! 227: .Ar list ! 228: .Cx \&\ \& ! 229: .Ic then ! 230: .Cx \&\ \& ! 231: .Ar list ! 232: .Cx \&\ \& ! 233: .Op Ic elif Ar list Ic then Ar list ! 234: .Cx \&\ \& ! 235: .Cx \&... ! 236: .Cx \&\ \& ! 237: .Op Ic else Ar list ! 238: .Cx \&\ \& ! 239: .Ic fi ! 240: .Cx ! 241: The ! 242: .Ar list ! 243: following ! 244: .Ic if ! 245: is executed and if it returns zero the ! 246: .Ar list ! 247: following ! 248: .Ic then ! 249: is executed. Otherwise, the ! 250: .Ar list ! 251: following ! 252: .Ic elif ! 253: is executed and if its value is zero the ! 254: .Ar list ! 255: following ! 256: .Ic then ! 257: is executed. Failing that the ! 258: .Ic else ! 259: .Ar list ! 260: is executed. ! 261: .Tp Cx Ic while ! 262: .Cx \&\ \& ! 263: .Ar list ! 264: .Cx \&\ \& ! 265: .Op Ic do Ar list ! 266: .Cx \&\ \& ! 267: .Ic done ! 268: .Cx ! 269: A ! 270: .Ic while ! 271: command repeatedly executes the ! 272: .Ic while ! 273: .Ar list ! 274: and if its value is zero executes the ! 275: .Ic do ! 276: .Ar list ; ! 277: otherwise the loop terminates. The value returned by a ! 278: .Ic while ! 279: command is that of the last executed command in the ! 280: .Ic do ! 281: .Ar list . ! 282: .Ic until ! 283: may be used in place of ! 284: .Ic while ! 285: to negate the loop termination test. ! 286: .Tp Pq Ar list ! 287: Execute ! 288: .Ar list ! 289: in a subshell. ! 290: .Tp Cx \&{ ! 291: .Ar list ! 292: .Cx \&} ! 293: .Cx ! 294: .Ar list ! 295: is simply executed. ! 296: .Tp ! 297: .Pp ! 298: The following words are only recognized as the first word of a command ! 299: and when not quoted. ! 300: .Df I ! 301: .Nm if then else elif fi case in esac ! 302: .Nm for while until do done \&{ \&} ! 303: .De ! 304: .Pp ! 305: .Ss Command substitution ! 306: The standard output from a command enclosed in a pair of back quotes ! 307: .Pq Ic \&`` ! 308: may be used as part or all of a word; trailing newlines are removed. ! 309: .Pp ! 310: .Ss Parameter substitution . ! 311: The character ! 312: .Ic \&$ ! 313: is used to introduce substitutable parameters. ! 314: Positional parameters may be assigned values by ! 315: .Ic set . ! 316: Variables may be set by writing ! 317: .Pp ! 318: .Df I ! 319: .Ar name=value ! 320: .Op Ar name=value ! 321: \&... ! 322: .De ! 323: .Pp ! 324: .Tp Cx Ic \&$ ! 325: .Cx \&\ \& ! 326: .Sy \&{ ! 327: .Ar parameter ! 328: .Sy \&} ! 329: .Cx ! 330: A ! 331: .Ar parameter ! 332: is a sequence of letters, digits or underscores (a ! 333: .Ar name ) , ! 334: a digit, or any of the characters ! 335: .Nm \&* \&@ \&# \&? \&\- \&$ \&!\ ! 336: The value, if any, of the parameter is substituted. ! 337: The braces are required only when ! 338: .Ar parameter ! 339: is followed by a letter, digit, or underscore ! 340: that is not to be interpreted as part of its name. If ! 341: .Ar parameter ! 342: is a digit, it is a positional parameter. If ! 343: .Ar parameter ! 344: is ! 345: .Ic \&* ! 346: or ! 347: .Ic \&@ ! 348: then all the positional parameters, starting with ! 349: .Ic $1 , ! 350: are substituted separated by spaces. ! 351: .Ic $0 ! 352: is set from argument zero when the shell is invoked. ! 353: .Tp Cx Ic \&$ ! 354: .Cx \&\ \& ! 355: .Sy \&{ ! 356: .Ar parameter ! 357: .Fl ! 358: .Ar word ! 359: .Sy \&} ! 360: .Cx ! 361: If ! 362: .Ar parameter ! 363: is set, substitute its value; otherwise substitute ! 364: .Ar word . ! 365: .Tp Cx Ic \&$ ! 366: .Cx \&\ \& ! 367: .Sy \&{ ! 368: .Ar parameter ! 369: .Ic \&= ! 370: .Ar word ! 371: .Cx \&\ \& ! 372: .Sy \&} ! 373: .Cx ! 374: If ! 375: .Ar parameter ! 376: is not set, set it to ! 377: .Ar word ; ! 378: the value of the parameter is then substituted. ! 379: Positional parameters may not be assigned to in this way. ! 380: .Tp Cx Ic \&$ ! 381: .Cx \&\ \& ! 382: .Sy \&{ ! 383: .Ar parameter ! 384: .Ic \&? ! 385: .Ar word ! 386: .Sy \&} ! 387: .Cx ! 388: If ! 389: .Ar parameter ! 390: is set, substitute its value; otherwise, print ! 391: .Ar word ! 392: and exit from the shell. If ! 393: .Ar word ! 394: is omitted, a standard message is printed. ! 395: .Tp Cx Ic \&$ ! 396: .Cx \&\ \& ! 397: .Sy \&{ ! 398: .Ar parameter ! 399: .Ic \&+ ! 400: .Ar word ! 401: .Sy \&} ! 402: .Cx ! 403: If ! 404: .Ar parameter ! 405: is set, substitute ! 406: .Ar word ; ! 407: otherwise substitute nothing. ! 408: .Tp ! 409: .Pp ! 410: In the above ! 411: .Ar word ! 412: is not evaluated unless it is to be used as the substituted string. ! 413: (So that, for example, echo ${d\-\'pwd\'} will only execute ! 414: .Ar pwd ! 415: if ! 416: .Ar d ! 417: is unset.) ! 418: .Pp ! 419: The following ! 420: .Ar parameters ! 421: are automatically set by the shell. ! 422: .Pp ! 423: .Dw Ds ! 424: .Dp Ic \&# ! 425: The number of positional parameters in decimal. ! 426: .Dp Fl ! 427: Options supplied to the shell on invocation or by ! 428: .Ar set . ! 429: .Dp Ic \&? ! 430: The value returned by the last executed command in decimal. ! 431: .Dp Ic \&$ ! 432: The process number of this shell. ! 433: .Dp Ic \&! ! 434: The process number of the last background command invoked. ! 435: .Dp ! 436: .De ! 437: .Pp ! 438: The following ! 439: .Ar parameters ! 440: are used but not set by the shell. ! 441: .Pp ! 442: .Ds I ! 443: .Tp Ev HOME ! 444: The default argument (home directory) for the ! 445: .Ic cd ! 446: command. ! 447: .Tp Ev PATH ! 448: The search path for commands (see ! 449: .Ar execution ) . ! 450: .Tp Ev MAIL ! 451: If this variable is set to the name of ! 452: a mail file, the shell informs the user of ! 453: the arrival of mail in the specified file. ! 454: .Tp Ev PS1 ! 455: Primary prompt string, by default '$ '. ! 456: .Tp Ev PS2 ! 457: Secondary prompt string, by default '> '. ! 458: .Tp Ev IFS ! 459: Internal field separators, normally ! 460: .Em space , ! 461: .Em tab , ! 462: and ! 463: .Em newline . ! 464: .Ev IFS ! 465: is ignored if ! 466: .Nm sh ! 467: is running as root or if the effective user id differs from the real user id. ! 468: .Tp ! 469: .De ! 470: .Ss Blank interpretation . ! 471: After parameter and command substitution, ! 472: any results of substitution are scanned for internal field separator ! 473: characters (those found in ! 474: .Cx Ic $ ! 475: .Ev IFS ) ! 476: .Cx ! 477: and split into distinct arguments where such characters are found. ! 478: Explicit null arguments ("" or \'\') are retained. ! 479: Implicit null arguments (those resulting from ! 480: .Em parameters ! 481: that have no values) are removed. ! 482: .Pp ! 483: .Ss File name generation . ! 484: Following substitution, each command word is scanned for the characters ! 485: .Ic \&* , ! 486: .Ic \&? ! 487: and ! 488: .Ic \&[ . ! 489: If one of these characters appears, the word is regarded as a pattern. ! 490: The word is replaced with alphabetically sorted file names that match the ! 491: pattern. If no file name is found that matches the pattern, ! 492: the word is left unchanged. The character ! 493: .Ic \&. ! 494: at the start of a file name or immediately following a ! 495: .Ic \&/ , ! 496: and the character ! 497: .Ic \&/ , ! 498: must be matched explicitly. ! 499: .Dp Ic \&*\& ! 500: Matches any string, including the null string. ! 501: .Dp Ic \&? ! 502: Matches any single character. ! 503: .Dp Ic \&[...] ! 504: Matches any one of the characters enclosed. ! 505: A pair of characters separated by ! 506: .Fl ! 507: matches any character lexically between the pair. ! 508: .Dp ! 509: .Pp ! 510: .Ss Quoting . ! 511: The following characters have a special meaning to the shell ! 512: and cause termination of a word unless quoted. ! 513: .Pp ! 514: .Df I ! 515: .Sy \&; \&& \&( \&) \&| \&< \&> ! 516: .Sy newline space tab ! 517: .De ! 518: .Pp ! 519: A character may be ! 520: .Ar quoted ! 521: by preceding it with a ! 522: .Sq Sy \e . ! 523: .Sy \enewline ! 524: is ignored. ! 525: All characters enclosed between a pair of quote marks ! 526: .Pq Sq , ! 527: except a single quote, are quoted. Inside double quotes ! 528: .Pq Dq ! 529: parameter and command substitution occurs and ! 530: .Sy \e ! 531: quotes the characters ! 532: .Sy \e\' " ! 533: and ! 534: .Sy \&$ . ! 535: .Pp ! 536: .Dq \&$* ! 537: is equivalent to ! 538: .Dq Sy $1 $2 \&... ! 539: whereas ! 540: .br ! 541: .Dq Sy $@ ! 542: is equivalent to ! 543: .Dq Sy $1 ! 544: .Dq Sy $2 ! 545: \&...\ . ! 546: .Pp ! 547: .Ss Prompting . ! 548: When used interactively, the shell prompts with the value of ! 549: .Ev PS1 ! 550: before reading a command. ! 551: If at any time a newline is typed and further input is needed ! 552: to complete a command, the secondary prompt ! 553: .Cx Sy $ ! 554: .Ev PS2 ! 555: .Cx ! 556: is issued. ! 557: .Pp ! 558: .Ss Input/Output . ! 559: Before a command is executed its input and output ! 560: may be redirected using a special notation interpreted by the shell. ! 561: The following may appear anywhere in a simple-command ! 562: or may precede or follow a ! 563: .Ar command ! 564: and are not passed on to the invoked command. ! 565: Substitution occurs before ! 566: .Ar word ! 567: or ! 568: .Ar digit ! 569: is used. ! 570: .Tw Ic ! 571: .Tp Cx Ic \&< ! 572: .Cx \&\ \& ! 573: .Ar word ! 574: .Cx ! 575: Use file ! 576: .Ar word ! 577: as standard input (file descriptor 0). ! 578: .Tp Cx Ic \&> ! 579: .Cx \&\ \& ! 580: .Ar word ! 581: .Cx ! 582: Use file ! 583: .Ar word ! 584: as standard output (file descriptor 1). ! 585: If the file does not exist, it is created; ! 586: otherwise it is truncated to zero length. ! 587: .Tp Cx Ic \&>\&> ! 588: .Cx \&\ \& ! 589: .Ar word ! 590: .Cx ! 591: Use file ! 592: .Ar word ! 593: as standard output. ! 594: If the file exists, output is appended (by seeking to the end); ! 595: otherwise the file is created. ! 596: .Tp Cx Ic \&<\&< ! 597: .Cx \&\ \& ! 598: .Ar word ! 599: .Cx ! 600: The shell input is read up to a line the same as ! 601: .Ar word , ! 602: or end of file. ! 603: The resulting document becomes the standard input. ! 604: If any character of ! 605: .Ar word ! 606: is quoted, no interpretation is placed upon the characters of the document; ! 607: otherwise, parameter and command substitution occurs, ! 608: .Sy \enewline ! 609: is ignored, and ! 610: .Sy \e ! 611: is used to quote the characters ! 612: .Sy \&$ \&\' ! 613: and the first character of ! 614: .Ar word . ! 615: .Tp Cx Ic \&<\&& ! 616: .Cx \&\ \& ! 617: .Ar digit ! 618: .Cx ! 619: The standard input is duplicated from file descriptor ! 620: .Ar digit ; ! 621: see ! 622: .Xr dup 2 . ! 623: Similarly for the standard output using ! 624: .Ic \&> . ! 625: .Tp Ic \&<\&&\- ! 626: The standard input is closed. ! 627: Similarly for the standard output using ! 628: .Ic \&> . ! 629: .Tp ! 630: .Pp ! 631: If one of the above is preceded by a digit, the ! 632: file descriptor created is that specified by the digit ! 633: (instead of the default 0 or 1). For example, ! 634: .Pp ! 635: .Dl \&... 2>&1 ! 636: .Pp ! 637: creates file descriptor 2 to be a duplicate ! 638: of file descriptor 1. ! 639: .Pp ! 640: If a command is followed by ! 641: .Ic \&& ! 642: then the default standard input for the command is the empty file ! 643: .Pq Pa dev/null . ! 644: Otherwise, the environment for the execution of a command contains the ! 645: file descriptors of the invoking shell as modified by input ! 646: output specifications. ! 647: .Pp ! 648: .Ss Environment ! 649: The environment is a list of name-value pairs that is passed to ! 650: an executed program in the same way as a normal argument list; see ! 651: .Xr execve 2 ! 652: and ! 653: .Xr environ 7 . ! 654: The shell interacts with the environment in several ways. ! 655: On invocation, the shell scans the environment and creates a ! 656: .Ar parameter ! 657: for each name found, giving it the corresponding value. ! 658: Executed commands inherit the same environment. ! 659: If the user modifies the values of these ! 660: .Ar parameters ! 661: or creates new ones, none of these affects the environment unless the ! 662: .Ic export ! 663: command is used to bind the shell's ! 664: .Ar parameter ! 665: to the environment. ! 666: The environment seen by any executed command is thus composed ! 667: of any unmodified name-value pairs originally inherited by the shell, ! 668: plus any modifications or additions, all of which must be noted in ! 669: .Ic export ! 670: commands. ! 671: .Pp ! 672: The environment for any ! 673: .Ar simple-command ! 674: may be augmented by prefixing it with one or more assignments to ! 675: .Ar parameters . ! 676: Thus these two lines are equivalent ! 677: .Pp ! 678: .Dl TERM=450 cmd args ! 679: .Dl (export TERM; TERM=450; cmd args) ! 680: .Pp ! 681: If the ! 682: .Fl k ! 683: flag is set, ! 684: .Ar all ! 685: keyword arguments are placed in the environment, ! 686: even if they occur after the command name. ! 687: The following prints 'a=b c' and 'c': ! 688: .Pp ! 689: .Ds I ! 690: echo a=b c ! 691: set \-k ! 692: echo a=b c ! 693: .De ! 694: .Pp ! 695: .Ss Signals . ! 696: The INTERRUPT and QUIT signals for an invoked ! 697: command are ignored if the command is followed by ! 698: .Ic \&& ; ! 699: otherwise signals have the values inherited by the shell from its parent. ! 700: (But see also ! 701: .Ic trap . ) ! 702: .Pp ! 703: .Ss Execution . ! 704: Each time a command is executed the above substitutions are carried out. ! 705: Except for the 'special commands' listed below a new process is created and ! 706: an attempt is made to execute the command via an ! 707: .Xr execve 2 . ! 708: .Pp ! 709: The shell parameter ! 710: .Cx Ic \&$ ! 711: .Ev $PATH ! 712: .Cx ! 713: defines the search path for the directory containing the command. ! 714: Each alternative directory name is separated by a colon ! 715: .Pq Sy \&: . ! 716: The default path is ! 717: .Pa :/bin:/usr/bin . ! 718: If the command name contains a ! 719: .Sy / , ! 720: the search path is not used. ! 721: Otherwise, each directory in the path is searched for an executable file. ! 722: If the file has execute permission but is not an ! 723: .Pa a.out ! 724: file, it is assumed to be a file containing shell commands. ! 725: A subshell (i.e., a separate process) is spawned to read it. ! 726: A parenthesized command is also executed in a subshell. ! 727: .Pp ! 728: .Ss Special commands . ! 729: The following commands are executed in the shell process ! 730: and except where specified ! 731: no input output redirection is permitted for such commands. ! 732: .Tw Fl ! 733: .Tp Ic \&# ! 734: For non-interactive shells, everything following the ! 735: .Ic \&# ! 736: is treated as a comment, i.e. the rest of the line is ignored. ! 737: For interactive shells, the ! 738: .Ic \&# ! 739: has no special effect. ! 740: .Tp Ic \&:\& ! 741: No effect; the command does nothing. ! 742: .Tp Cx Ic \&.\& ! 743: .Ar file ! 744: .Cx ! 745: Read and execute commands from ! 746: .Ar file ! 747: and return. The search path ! 748: .Cx Ic \&$ ! 749: .Ev PATH ! 750: .Cx ! 751: is used to find the directory containing ! 752: .Ar file . ! 753: .Tp Cx Ic break ! 754: .Cx \&\ \& ! 755: .Op Ar n ! 756: .Cx ! 757: Exit from the enclosing ! 758: .Ic for ! 759: or ! 760: .Ic while ! 761: loop, if any. ! 762: If ! 763: .Ar n ! 764: is specified, break ! 765: .Ar n ! 766: levels. ! 767: .Tp Cx Ic continue ! 768: .Cx \&\ \& ! 769: .Op Ar n ! 770: .Cx ! 771: Resume the next iteration of the enclosing ! 772: .Ic for ! 773: or ! 774: .Ic while ! 775: loop. If ! 776: .Ar n ! 777: is specified, resume at the ! 778: .Cx Ar n ! 779: .Cx \'th ! 780: .Cx ! 781: enclosing loop. ! 782: .Tp Cx Ic cd ! 783: .Cx \&\ \& ! 784: .Op Ar arg ! 785: .Cx ! 786: Change the current directory to ! 787: .Ar arg . ! 788: The shell parameter ! 789: .Cx Sy \&$ ! 790: .Ev $HOME ! 791: .Cx ! 792: is the default ! 793: .Ar arg . ! 794: .Tp Cx Ic eval ! 795: .Cx \&\ \& ! 796: .Op Ar arg \&... ! 797: .Cx ! 798: The arguments are read as input to the shell ! 799: and the resulting command(s) executed. ! 800: .Tp Cx Ic exec ! 801: .Cx \&\ \& ! 802: .Op Ar arg \&... ! 803: .Cx ! 804: The command specified by the arguments is executed in place of this shell ! 805: without creating a new process. ! 806: Input output arguments may appear and if no other ! 807: arguments are given cause the shell input output to be modified. ! 808: .Tp Cx Ic exit ! 809: .Cx \&\ \& ! 810: .Op Ar n ! 811: .Cx ! 812: Causes a non interactive shell to exit with the exit status specified by ! 813: .Ar n . ! 814: If ! 815: .Ar n ! 816: is omitted, the exit status is that of the last command executed. ! 817: (An end of file will also exit from the shell.) ! 818: .Tp Cx Ic export ! 819: .Cx \&\ \& ! 820: .Op Ar name ... ! 821: .Cx ! 822: The given names are marked for automatic export to the ! 823: .Ar environment ! 824: of subsequently-executed commands. ! 825: If no arguments are given, a list of exportable names is printed. ! 826: .Tp Cx Ic login ! 827: .Cx \&\ \& ! 828: .Op Ar arg ... ! 829: .Cx ! 830: Equivalent to 'exec login arg ...'. ! 831: .Tp Cx Ic read ! 832: .Cx \&\ \& ! 833: .Ar name \&... ! 834: .Cx ! 835: One line is read from the standard input; ! 836: successive words of the input are assigned to the variables ! 837: .Ar name ! 838: in order, with leftover words to the last variable. ! 839: The return code is 0 unless the end-of-file is encountered. ! 840: .Tp Cx Ic readonly ! 841: .Cx \&\ \& ! 842: .Op Ar name \&... ! 843: .Cx ! 844: The given names are marked readonly and ! 845: the values of the these names may not be changed ! 846: by subsequent assignment. ! 847: If no arguments are given, a list of all readonly names is printed. ! 848: .Tp Cx Ic set ! 849: .Cx \&\ \& ! 850: .Op Fl eknptuvx ! 851: .Cx \&\ \& ! 852: .Op Ar arg ... ! 853: .Cx ! 854: The set flags are described in the options section at the beginning ! 855: of this man page. ! 856: The current set of flags may be found in ! 857: .Ic \&$\- . ! 858: .Pp ! 859: Remaining arguments after the flag are positional ! 860: parameters and are assigned, in order, to ! 861: .Ic \&$1 , ! 862: .Ic \&$2 , ! 863: etc. If no arguments are given, the values of all names are printed. ! 864: .Tp Ic shift ! 865: The positional parameters from ! 866: .Ic \&$2 ... ! 867: are renamed ! 868: .Ic $1 ... ! 869: .Tp Ic times ! 870: Print the accumulated user and system times for processes run from the shell. ! 871: .Tp Cx Ic trap ! 872: .Cx \&\ \& ! 873: .Op Ar arg ! 874: .Cx \&\ \& ! 875: .Op Ar n ! 876: .Cx \&\ \& \&... ! 877: .Cx ! 878: .Ar Arg ! 879: is a command to be read and executed when the shell receives signal(s) ! 880: .Ar n . ! 881: (Note that ! 882: .Ar arg ! 883: is scanned once when the trap is set and once when the trap is taken.) ! 884: Trap commands are executed in order of signal number. If ! 885: .Ar arg ! 886: is absent, all trap(s) ! 887: .Ar n ! 888: are reset to their original values. ! 889: If ! 890: .Ar arg ! 891: is the null ! 892: string, this signal is ignored by the shell and by invoked commands. ! 893: If ! 894: .Ar n ! 895: is 0, the command ! 896: .Ar arg ! 897: is executed on exit from the shell, otherwise upon receipt of signal ! 898: .Ar n ! 899: as numbered in ! 900: .Xr sigvec 2 . ! 901: .Ic Trap ! 902: with no arguments prints a list of commands associated with each signal number. ! 903: .Tp Cx Ic umask ! 904: .Cx \&\ \& ! 905: .Op Ar nnn ! 906: .Cx ! 907: The user file creation mask is set to the octal value ! 908: .Ar nnn ! 909: (see ! 910: .Xr umask 2 ) . ! 911: If ! 912: .Ar nnn ! 913: is omitted, the current value of the mask is printed. ! 914: .Tp Cx Ic wait ! 915: .Cx \&\ \& ! 916: .Op Ar n ! 917: .Cx ! 918: Wait for the specified process and report its termination status. If ! 919: .Ar n ! 920: is not given, all currently active child processes are waited for. ! 921: The return code from this command is that of the process waited for. ! 922: .Tp ! 923: .Sh FILES ! 924: .Dw (longest file name here) ! 925: .Di L ! 926: .Dp Pa $HOME/.profile ! 927: .Dp Pa /tmp/sh* ! 928: .Dp Pa /dev/null ! 929: .Dp ! 930: .Sh SEE ALSO ! 931: .Xr csh 1 , ! 932: .Xr test 1 , ! 933: .Xr execve 2 , ! 934: .Xr environ 7 ! 935: .Sh DIAGNOSTICS ! 936: Errors detected by the shell, such as syntax errors cause the shell ! 937: to return a non zero exit status. ! 938: If the shell is being used non interactively ! 939: then execution of the shell file is abandoned. ! 940: Otherwise, the shell returns the exit status of ! 941: the last command executed (see also ! 942: .Ic exit ) . ! 943: .Sh HISTORY ! 944: The ! 945: .Nm Sh ! 946: shell appeared in Version 6 AT&Y UNIX. ! 947: .SH BUGS ! 948: If ! 949: .Ic \&<\&< ! 950: is used to provide standard input to an asynchronous ! 951: process invoked by ! 952: .Ic \&& , ! 953: the shell gets mixed up about naming the input document. ! 954: A garbage file ! 955: .Pa /tmp/sh* ! 956: is created, and the shell complains about ! 957: not being able to find the file by another name. ! 958: .\" .Sh ENVIRONMENT ! 959: .\" /usr/src/bin/sh/defs.h:STRING *setenv(); ! 960: .\" /usr/src/bin/sh/name.c:STRING *setenv() ! 961: .\" /usr/src/bin/sh/service.c: xecenv=setenv();
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