Annotation of src/usr.bin/awk/awk.1, Revision 1.18
1.18 ! jmc 1: .\" $OpenBSD: awk.1,v 1.17 2003/12/16 11:18:37 jmc Exp $
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1.7 aaron 26: .Dd June 29, 1996
27: .Dt AWK 1
28: .Os
29: .Sh NAME
30: .Nm awk
31: .Nd pattern-directed scanning and processing language
32: .Sh SYNOPSIS
33: .Nm awk
1.16 jmc 34: .Op Fl safe
35: .Op Fl V
36: .Op Fl d Ns Op Ar n
1.7 aaron 37: .Op Fl F Ar fs
1.16 jmc 38: .Oo Fl v Ar var Ns =
39: .Ns Ar value Oc
1.18 ! jmc 40: .Op Ar prog | Fl f Ar progfile
1.7 aaron 41: .Ar
42: .Nm nawk
43: .Ar ...
44: .Sh DESCRIPTION
45: .Nm
1.1 tholo 46: scans each input
1.7 aaron 47: .Ar file
1.1 tholo 48: for lines that match any of a set of patterns specified literally in
1.7 aaron 49: .Ar prog
1.16 jmc 50: or in one or more files specified as
1.7 aaron 51: .Fl f Ar progfile .
1.16 jmc 52: With each pattern there can be an associated action that will be performed
1.1 tholo 53: when a line of a
1.7 aaron 54: .Ar file
1.1 tholo 55: matches the pattern.
56: Each line is matched against the
57: pattern portion of every pattern-action statement;
58: the associated action is performed for each matched pattern.
1.6 aaron 59: The file name
1.16 jmc 60: .Sq -
1.1 tholo 61: means the standard input.
62: Any
1.7 aaron 63: .Ar file
1.1 tholo 64: of the form
1.16 jmc 65: .Ar var Ns = Ns Ar value
1.1 tholo 66: is treated as an assignment, not a filename,
67: and is executed at the time it would have been opened if it were a filename.
1.16 jmc 68: .Pp
69: The options are as follows:
70: .Bl -tag -width Ds
71: .It Fl d Ns Op Ar n
72: Debug mode.
73: Set debug level to
74: .Ar n ,
75: or 1 if
76: .Ar n
77: is not specified.
78: A value greater than 1 causes
79: .Nm
80: to dump core on fatal errors.
81: .It Fl F Ar fs
82: Define the input field separator to be the regular expression
1.7 aaron 83: .Ar fs .
1.16 jmc 84: .It Fl f Ar filename
85: Read program code from the specified file
86: .Ar filename
87: instead of from the command line.
88: .It Fl safe
89: Disable file output
1.17 jmc 90: .Pf ( Ic print No > ,
91: .Ic print No >> ) ,
1.7 aaron 92: process creation
93: .Po
1.17 jmc 94: .Ar cmd | Ic getline ,
95: .Ic print No \&| ,
96: .Ic system
1.7 aaron 97: .Pc
98: and access to the environment
1.17 jmc 99: .Pf ( Va ENVIRON ;
1.18 ! jmc 100: see the section on variables below).
1.17 jmc 101: This is a first
1.16 jmc 102: .Pq and not very reliable
103: approximation to a
1.7 aaron 104: .Dq safe
105: version of
1.16 jmc 106: .Nm .
107: .It Fl V
108: Print the version number of
109: .Nm
110: to standard output and exit.
111: .It Fl v Ar var Ns = Ns Ar value
112: Assign
113: .Ar value
114: to variable
115: .Ar var
116: before
117: .Ar prog
118: is executed;
119: any number of
120: .Fl v
121: options may be present.
122: .El
1.7 aaron 123: .Pp
1.18 ! jmc 124: The input is normally made up of input lines
! 125: .Pq records
! 126: separated by newlines, or by the value of
! 127: .Va RS .
! 128: If
! 129: .Va RS
! 130: is null, then any number of blank lines are used as the record separator,
! 131: and newlines are used as field separators
! 132: (in addition to the value of
! 133: .Va FS ) .
! 134: This is convenient when working with multi-line records.
! 135: .Pp
1.7 aaron 136: An input line is normally made up of fields separated by whitespace,
1.18 ! jmc 137: or by the regular expression
1.7 aaron 138: .Va FS .
1.1 tholo 139: The fields are denoted
1.7 aaron 140: .Va $1 , $2 , ... ,
141: while
142: .Va $0
1.1 tholo 143: refers to the entire line.
144: If
1.7 aaron 145: .Va FS
1.1 tholo 146: is null, the input line is split into one field per character.
1.7 aaron 147: .Pp
1.18 ! jmc 148: Normally, any number of blanks separate fields.
! 149: In order to set the field separator to a single blank, use the
! 150: .Fl F
! 151: option with a value of
! 152: .Sq [\ \&] .
! 153: If a field separator of
! 154: .Sq t
! 155: is specified,
! 156: .Nm
! 157: treats it as if
! 158: .Sq \et
! 159: had been specified and uses
! 160: .Aq TAB
! 161: as the field separator.
! 162: In order to use a literal
! 163: .Sq t
! 164: as the field separator, use the
! 165: .Fl F
! 166: option with a value of
! 167: .Sq [t] .
! 168: .Pp
1.1 tholo 169: A pattern-action statement has the form
1.7 aaron 170: .Pp
171: .D1 Ar pattern Ic \&{ Ar action Ic \&}
172: .Pp
1.6 aaron 173: A missing
1.7 aaron 174: .Ic \&{ Ar action Ic \&}
1.1 tholo 175: means print the line;
176: a missing pattern always matches.
177: Pattern-action statements are separated by newlines or semicolons.
1.7 aaron 178: .Pp
1.18 ! jmc 179: Newlines are permitted after a terminating statement or following a comma
! 180: .Pq Sq ,\& ,
! 181: an open brace
! 182: .Pq Sq { ,
! 183: a logical AND
! 184: .Pq Sq && ,
! 185: a logical OR
! 186: .Pq Sq || ,
! 187: after the
! 188: .Sq do
! 189: or
! 190: .Sq else
! 191: keywords,
! 192: or after the closing parenthesis of an
! 193: .Sq if ,
! 194: .Sq for ,
! 195: or
! 196: .Sq while
! 197: statement.
! 198: Additionally, a backslash
! 199: .Pq Sq \e
! 200: can be used to escape a newline between tokens.
! 201: .Pp
1.1 tholo 202: An action is a sequence of statements.
203: A statement can be one of the following:
1.7 aaron 204: .Bd -unfilled -offset indent
205: .Ic if ( Xo
206: .Ar expression ) statement \&
207: .Op Ic else Ar statement
208: .Xc
209: .Ic while ( Ar expression ) statement
210: .Ic for ( Xo
211: .Ar expression ; expression ; expression ) statement
212: .Xc
213: .Ic for ( Xo
214: .Ar var Ic in Ar array ) statement
215: .Xc
216: .Ic do Ar statement Ic while ( Ar expression )
217: .Ic break
218: .Ic continue
219: .Ic { Oo Ar statement ... Oc Ic \& }
220: .Ar expression Xo
221: .No "# commonly" \&
222: .Ar var Ic = Ar expression
223: .Xc
224: .Ic print Xo
225: .Op Ar expression-list
1.17 jmc 226: .Op > Ns Ar expression
1.7 aaron 227: .Xc
228: .Ic printf Ar format Xo
229: .Op Ar ... , expression-list
1.17 jmc 230: .Op > Ns Ar expression
1.7 aaron 231: .Xc
232: .Ic return Op Ar expression
233: .Ic next Xo
234: .No "# skip remaining patterns on this input line"
235: .Xc
236: .Ic nextfile Xo
237: .No "# skip rest of this file, open next, start at top"
238: .Xc
239: .Ic delete Ar array Ns Xo
240: .Ic \&[ Ns Ar expression Ns Ic \&]
241: .No \& "# delete an array element"
242: .Xc
243: .Ic delete Ar array Xo
244: .No "# delete all elements of array"
245: .Xc
246: .Ic exit Xo
247: .Op Ar expression
248: .No \& "# exit immediately; status is" Ar expression
249: .Xc
250: .Ed
251: .Pp
1.1 tholo 252: Statements are terminated by
253: semicolons, newlines or right braces.
254: An empty
1.7 aaron 255: .Ar expression-list
1.1 tholo 256: stands for
1.7 aaron 257: .Ar $0 .
258: String constants are quoted
259: .Li \&"" ,
1.1 tholo 260: with the usual C escapes recognized within.
261: Expressions take on string or numeric values as appropriate,
262: and are built using the operators
1.7 aaron 263: .Ic + \- * / % ^
264: (exponentiation), and concatenation (indicated by whitespace).
1.1 tholo 265: The operators
1.16 jmc 266: .Ic \&! ++ \-\- += \-= *= /= %= ^=
267: .Ic > >= < <= == != ?:
1.1 tholo 268: are also available in expressions.
269: Variables may be scalars, array elements
270: (denoted
1.7 aaron 271: .Li x[i] )
1.1 tholo 272: or fields.
273: Variables are initialized to the null string.
274: Array subscripts may be any string,
275: not necessarily numeric;
276: this allows for a form of associative memory.
277: Multiple subscripts such as
1.7 aaron 278: .Li [i,j,k]
1.1 tholo 279: are permitted; the constituents are concatenated,
280: separated by the value of
1.17 jmc 281: .Va SUBSEP
1.18 ! jmc 282: .Pq see the section on variables below ) .
1.7 aaron 283: .Pp
1.1 tholo 284: The
1.7 aaron 285: .Ic print
1.1 tholo 286: statement prints its arguments on the standard output
287: (or on a file if
1.17 jmc 288: .Pf > Ns Ar file
1.1 tholo 289: or
1.17 jmc 290: .Pf >> Ns Ar file
1.1 tholo 291: is present or on a pipe if
1.17 jmc 292: .Pf |\ \& Ar cmd
1.1 tholo 293: is present), separated by the current output field separator,
294: and terminated by the output record separator.
1.7 aaron 295: .Ar file
1.1 tholo 296: and
1.7 aaron 297: .Ar cmd
1.1 tholo 298: may be literal names or parenthesized expressions;
299: identical string values in different statements denote
300: the same open file.
301: The
1.7 aaron 302: .Ic printf
1.1 tholo 303: statement formats its expression list according to the format
304: (see
1.10 pvalchev 305: .Xr printf 3 ) .
1.18 ! jmc 306: .Pp
! 307: Patterns are arbitrary Boolean combinations
! 308: (with
! 309: .Ic "\&! || &&" )
! 310: of regular expressions and
! 311: relational expressions.
! 312: Regular expressions are as in
! 313: .Xr egrep 1 .
! 314: Isolated regular expressions
! 315: in a pattern apply to the entire line.
! 316: Regular expressions may also occur in
! 317: relational expressions, using the operators
! 318: .Ic ~
! 319: and
! 320: .Ic !~ .
! 321: .Pf / Ns Ar re Ns /
! 322: is a constant regular expression;
! 323: any string (constant or variable) may be used
! 324: as a regular expression, except in the position of an isolated regular expression
! 325: in a pattern.
! 326: .Pp
! 327: A pattern may consist of two patterns separated by a comma;
! 328: in this case, the action is performed for all lines
! 329: from an occurrence of the first pattern
! 330: through an occurrence of the second.
! 331: .Pp
! 332: A relational expression is one of the following:
! 333: .Bd -unfilled -offset indent
! 334: .Ar expression matchop regular-expression
! 335: .Ar expression relop expression
! 336: .Ar expression Ic in Ar array-name
! 337: .Ic \&( Ns Xo
! 338: .Ar expr , expr , \&... Ns Ic \&) in
! 339: .Ar \& array-name
! 340: .Xc
! 341: .Ed
! 342: .Pp
! 343: where a
! 344: .Ar relop
! 345: is any of the six relational operators in C, and a
! 346: .Ar matchop
! 347: is either
! 348: .Ic ~
! 349: (matches)
! 350: or
! 351: .Ic !~
! 352: (does not match).
! 353: A conditional is an arithmetic expression,
! 354: a relational expression,
! 355: or a Boolean combination
! 356: of these.
! 357: .Pp
! 358: The special patterns
! 359: .Ic BEGIN
! 360: and
! 361: .Ic END
! 362: may be used to capture control before the first input line is read
! 363: and after the last.
! 364: .Ic BEGIN
! 365: and
! 366: .Ic END
! 367: do not combine with other patterns.
! 368: .Pp
! 369: Variable names with special meanings:
! 370: .Pp
! 371: .Bl -tag -width "FILENAME" -compact
! 372: .It Va ARGC
! 373: Argument count, assignable.
! 374: .It Va ARGV
! 375: Argument array, assignable;
! 376: non-null members are taken as filenames.
! 377: .It Va CONVFMT
! 378: Conversion format when converting numbers
! 379: (default
! 380: .Qq Li %.6g ) .
! 381: .It Va ENVIRON
! 382: Array of environment variables; subscripts are names.
! 383: .It Va FILENAME
! 384: The name of the current input file.
! 385: .It Va FNR
! 386: Ordinal number of the current record in the current file.
! 387: .It Va FS
! 388: Regular expression used to separate fields; also settable
! 389: by option
! 390: .Fl F Ar fs .
! 391: .It Va NF
! 392: Number of fields in the current record.
! 393: .Va $NF
! 394: can be used to obtain the value of the last field in the current record.
! 395: .It Va NR
! 396: Ordinal number of the current record.
! 397: .It Va OFMT
! 398: Output format for numbers (default
! 399: .Qq Li %.6g ) .
! 400: .It Va OFS
! 401: Output field separator (default blank).
! 402: .It Va ORS
! 403: Output record separator (default newline).
! 404: .It Va RLENGTH
! 405: The length of the string matched by the
! 406: .Fn match
! 407: function.
! 408: .It Va RS
! 409: Input record separator (default newline).
! 410: .It Va RSTART
! 411: The starting position of the string matched by the
! 412: .Fn match
! 413: function.
! 414: .It Va SUBSEP
! 415: Separates multiple subscripts (default 034).
! 416: .El
1.17 jmc 417: .Sh FUNCTIONS
418: The awk language has a variety of built-in functions:
419: arithmetic, string, input/output and general.
420: .Ss Arithmetic Functions
421: .Bl -tag -width "atan2(y, x)"
422: .It Fn atan2 y x
423: Return the arctangent of
424: .Fa y Ns / Ns Fa x
425: in radians.
426: .It Fn cos x
427: Return the cosine of
428: .Fa x ,
429: where
430: .Fa x
431: is in radians.
432: .It Fn exp x
433: Return the exponential of
434: .Fa x .
435: .It Fn int x
436: Return
437: .Fa x
438: truncated to an integer value.
439: .It Fn log x
440: Return the natural logarithm of
441: .Fa x .
1.7 aaron 442: .It Fn rand
1.17 jmc 443: Return a random number,
444: .Fa n ,
445: such that
446: .Sm off
447: .Pf 0 \*(Le Fa n No \*(Lt 1 .
448: .Sm on
449: .It Fn sin x
450: Return the sine of
451: .Fa x ,
452: where
453: .Fa x
454: is in radians.
455: .It Fn sqrt x
456: Return the square root of
457: .Fa x .
458: .It Fn srand expr
1.16 jmc 459: Sets seed for
1.7 aaron 460: .Fn rand
1.17 jmc 461: to
462: .Fa expr
1.1 tholo 463: and returns the previous seed.
1.17 jmc 464: If
465: .Fa expr
466: is omitted, the time of day is used instead.
467: .El
468: .Ss String Functions
469: .Bl -tag -width "split(s, a, fs)"
470: .It Fn gsub r t s
471: The same as
472: .Fn sub
473: except that all occurrences of the regular expression are replaced.
474: .Fn gsub
475: returns the number of replacements.
1.7 aaron 476: .It Fn index s t
1.16 jmc 477: The position in
1.7 aaron 478: .Fa s
1.1 tholo 479: where the string
1.7 aaron 480: .Fa t
1.1 tholo 481: occurs, or 0 if it does not.
1.17 jmc 482: .It Fn length s
483: The length of
484: .Fa s
485: taken as a string,
486: or of
487: .Va $0
488: if no argument is given.
1.7 aaron 489: .It Fn match s r
1.16 jmc 490: The position in
1.7 aaron 491: .Fa s
1.1 tholo 492: where the regular expression
1.7 aaron 493: .Fa r
1.1 tholo 494: occurs, or 0 if it does not.
1.17 jmc 495: The variable
1.7 aaron 496: .Va RSTART
1.17 jmc 497: is set to the starting position of the matched string
498: .Pq which is the same as the returned value
499: or zero if no match is found.
500: The variable
1.7 aaron 501: .Va RLENGTH
1.17 jmc 502: is set to the length of the matched string,
503: or \-1 if no match is found.
1.7 aaron 504: .It Fn split s a fs
1.16 jmc 505: Splits the string
1.7 aaron 506: .Fa s
1.1 tholo 507: into array elements
1.7 aaron 508: .Va a[1] , a[2] , ... , a[n]
1.1 tholo 509: and returns
1.7 aaron 510: .Va n .
1.1 tholo 511: The separation is done with the regular expression
1.7 aaron 512: .Ar fs
1.1 tholo 513: or with the field separator
1.7 aaron 514: .Va FS
1.1 tholo 515: if
1.7 aaron 516: .Ar fs
1.1 tholo 517: is not given.
518: An empty string as field separator splits the string
519: into one array element per character.
1.17 jmc 520: .It Fn sprintf fmt expr ...
521: The string resulting from formatting
522: .Fa expr , ...
523: according to the
524: .Xr printf 3
525: format
526: .Fa fmt .
1.7 aaron 527: .It Fn sub r t s
1.16 jmc 528: Substitutes
1.7 aaron 529: .Fa t
1.1 tholo 530: for the first occurrence of the regular expression
1.7 aaron 531: .Fa r
1.1 tholo 532: in the string
1.7 aaron 533: .Fa s .
1.1 tholo 534: If
1.7 aaron 535: .Fa s
1.1 tholo 536: is not given,
1.7 aaron 537: .Va $0
1.1 tholo 538: is used.
1.17 jmc 539: An ampersand
540: .Pq Sq &
541: in
542: .Fa t
543: is replaced in string
544: .Fa s
545: with regular expression
546: .Fa r .
547: A literal ampersand can be specified by preceding it with two backslashes
548: .Pq Sq \e\e .
549: A literal backslash can be specified by preceding it with another backslash
550: .Pq Sq \e\e .
1.7 aaron 551: .Fn sub
1.17 jmc 552: returns the number of replacements.
553: .It Fn substr s m n
554: Return at most the
555: .Fa n Ns -character
556: substring of
557: .Fa s
558: that begins at position
559: .Fa m
560: counted from 1.
561: If
562: .Fa n
563: is omitted, or if
564: .Fa n
565: specifies more characters than are left in the string,
566: the length of the substring is limited by the length of
567: .Fa s .
1.7 aaron 568: .It Fn tolower str
1.16 jmc 569: Returns a copy of
1.7 aaron 570: .Fa str
1.1 tholo 571: with all upper-case characters translated to their
572: corresponding lower-case equivalents.
1.7 aaron 573: .It Fn toupper str
1.16 jmc 574: Returns a copy of
1.7 aaron 575: .Fa str
1.1 tholo 576: with all lower-case characters translated to their
577: corresponding upper-case equivalents.
1.7 aaron 578: .El
1.17 jmc 579: .Ss Input/Output and General Functions
580: .Bl -tag -width "getline [var] < file"
581: .It Fn close expr
582: Closes the file or pipe
583: .Fa expr .
584: .Fa expr
585: should match the string that was used to open the file or pipe.
586: .It Ar cmd | Ic getline Op Va var
587: Read a record of input from a stream piped from the output of
588: .Ar cmd .
589: If
590: .Va var
591: is omitted, the variables
592: .Va $0
593: and
594: .Va NF
595: are set.
596: Otherwise
597: .Va var
598: is set.
599: If the stream is not open, it is opened.
600: As long as the stream remains open, subsequent calls
601: will read subsequent records from the stream.
602: The stream remains open until explicitly closed with a call to
603: .Fn close .
604: .It Fn fflush expr
605: Flushes any buffered output for the file or pipe
606: .Fa expr .
607: .Fa expr
608: should match the string that was used to open the file or pipe.
609: .It Ic getline
610: Sets
611: .Va $0
612: to the next input record from the current input file.
613: This form of
614: .Ic getline
615: sets the variables
616: .Va NF ,
617: .Va NR ,
618: and
619: .Va FNR .
1.7 aaron 620: .Ic getline
1.17 jmc 621: returns 1 for a successful input, 0 for end of file, and \-1 for an error.
622: .It Ic getline Va var
623: Sets
1.7 aaron 624: .Va $0
1.17 jmc 625: to variable
626: .Va var .
627: This form of
628: .Ic getline
629: sets the variables
630: .Va NR
631: and
632: .Va FNR .
633: .Ic getline
634: returns 1 for a successful input, 0 for end of file, and \-1 for an error.
635: .It Xo
636: .Ic getline Op Va var
637: .Pf \ \&< Ar file
638: .Xc
639: Sets
1.7 aaron 640: .Va $0
1.1 tholo 641: to the next record from
1.7 aaron 642: .Ar file .
1.17 jmc 643: If
644: .Va var
645: is omitted, the variables
646: .Va $0
647: and
648: .Va NF
649: are set.
650: Otherwise
651: .Va var
652: is set.
653: If
654: .Ar file
655: is not open, it is opened.
656: As long as the stream remains open, subsequent calls will read subsequent
657: records from
658: .Ar file .
659: .Ar file
660: remains open until explicitly closed with a call to
661: .Fn close .
662: .It Fn system cmd
663: Executes
664: .Fa cmd
665: and returns its exit status.
666: .El
667: .Pp
668: Functions may be defined (at the position of a pattern-action statement)
669: thusly:
670: .Pp
671: .Dl function foo(a, b, c) { ...; return x }
1.7 aaron 672: .Pp
1.17 jmc 673: Parameters are passed by value if scalar, and by reference if array name;
674: functions may be called recursively.
675: Parameters are local to the function; all other variables are global.
676: Thus local variables may be created by providing excess parameters in
677: the function definition.
1.7 aaron 678: .Sh EXAMPLES
1.16 jmc 679: Print lines longer than 72 characters:
680: .Pp
1.7 aaron 681: .Dl length($0) > 72
1.16 jmc 682: .Pp
683: Print first two fields in opposite order:
1.7 aaron 684: .Pp
685: .Dl { print $2, $1 }
1.16 jmc 686: .Pp
687: Same, with input fields separated by comma and/or blanks and tabs:
1.7 aaron 688: .Bd -literal -offset indent
1.1 tholo 689: BEGIN { FS = ",[ \et]*|[ \et]+" }
690: { print $2, $1 }
1.7 aaron 691: .Ed
1.16 jmc 692: .Pp
693: Add up first column, print sum and average:
1.7 aaron 694: .Bd -literal -offset indent
695: { s += $1 }
696: END { print "sum is", s, " average is", s/NR }
697: .Ed
1.16 jmc 698: .Pp
699: Print all lines between start/stop pairs:
1.7 aaron 700: .Pp
701: .Dl /start/, /stop/
1.16 jmc 702: .Pp
703: Simulate echo(1):
1.7 aaron 704: .Bd -literal -offset indent
705: BEGIN { # Simulate echo(1)
706: for (i = 1; i < ARGC; i++) printf "%s ", ARGV[i]
707: printf "\en"
708: exit }
709: .Ed
710: .Sh SEE ALSO
1.16 jmc 711: .Xr egrep 1 ,
1.7 aaron 712: .Xr lex 1 ,
1.16 jmc 713: .Xr sed 1 ,
714: .Xr printf 3
1.7 aaron 715: .Rs
716: .%A A. V. Aho
717: .%A B. W. Kernighan
718: .%A P. J. Weinberger
719: .%T The AWK Programming Language
720: .%I Addison-Wesley
721: .%D 1988
722: .%O ISBN 0-201-07981-X
723: .Re
1.8 aaron 724: .Sh HISTORY
1.13 millert 725: An
1.8 aaron 726: .Nm
1.13 millert 727: utility appeared in
728: .At v7 .
1.7 aaron 729: .Sh BUGS
1.1 tholo 730: There are no explicit conversions between numbers and strings.
731: To force an expression to be treated as a number add 0 to it;
732: to force it to be treated as a string concatenate
1.7 aaron 733: .Li \&""
734: to it.
735: .Pp
1.1 tholo 736: The scope rules for variables in functions are a botch;
737: the syntax is worse.
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