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awk.1 (17547B)


      1 .\"	$OpenBSD: awk.1,v 1.41 2014/03/17 21:48:51 jmc Exp $
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     25 .Dd $Mdocdate: March 17 2014 $
     26 .Dt AWK 1
     27 .Os
     28 .Sh NAME
     29 .Nm awk
     30 .Nd pattern-directed scanning and processing language
     31 .Sh SYNOPSIS
     32 .Nm awk
     33 .Op Fl safe
     34 .Op Fl V
     35 .Op Fl d Ns Op Ar n
     36 .Op Fl F Ar fs
     37 .Op Fl v Ar var Ns = Ns Ar value
     38 .Op Ar prog | Fl f Ar progfile
     39 .Ar
     40 .Sh DESCRIPTION
     41 .Nm
     42 scans each input
     43 .Ar file
     44 for lines that match any of a set of patterns specified literally in
     45 .Ar prog
     46 or in one or more files specified as
     47 .Fl f Ar progfile .
     48 With each pattern there can be an associated action that will be performed
     49 when a line of a
     50 .Ar file
     51 matches the pattern.
     52 Each line is matched against the
     53 pattern portion of every pattern-action statement;
     54 the associated action is performed for each matched pattern.
     55 The file name
     56 .Sq -
     57 means the standard input.
     58 Any
     59 .Ar file
     60 of the form
     61 .Ar var Ns = Ns Ar value
     62 is treated as an assignment, not a filename,
     63 and is executed at the time it would have been opened if it were a filename.
     64 .Pp
     65 The options are as follows:
     66 .Bl -tag -width "-safe "
     67 .It Fl d Ns Op Ar n
     68 Debug mode.
     69 Set debug level to
     70 .Ar n ,
     71 or 1 if
     72 .Ar n
     73 is not specified.
     74 A value greater than 1 causes
     75 .Nm
     76 to dump core on fatal errors.
     77 .It Fl F Ar fs
     78 Define the input field separator to be the regular expression
     79 .Ar fs .
     80 .It Fl f Ar progfile
     81 Read program code from the specified file
     82 .Ar progfile
     83 instead of from the command line.
     84 .It Fl safe
     85 Disable file output
     86 .Pf ( Ic print No > ,
     87 .Ic print No >> ) ,
     88 process creation
     89 .Po
     90 .Ar cmd | Ic getline ,
     91 .Ic print | ,
     92 .Ic system
     93 .Pc
     94 and access to the environment
     95 .Pf ( Va ENVIRON ;
     96 see the section on variables below).
     97 This is a first
     98 .Pq and not very reliable
     99 approximation to a
    100 .Dq safe
    101 version of
    102 .Nm .
    103 .It Fl V
    104 Print the version number of
    105 .Nm
    106 to standard output and exit.
    107 .It Fl v Ar var Ns = Ns Ar value
    108 Assign
    109 .Ar value
    110 to variable
    111 .Ar var
    112 before
    113 .Ar prog
    114 is executed;
    115 any number of
    116 .Fl v
    117 options may be present.
    118 .El
    119 .Pp
    120 The input is normally made up of input lines
    121 .Pq records
    122 separated by newlines, or by the value of
    123 .Va RS .
    124 If
    125 .Va RS
    126 is null, then any number of blank lines are used as the record separator,
    127 and newlines are used as field separators
    128 (in addition to the value of
    129 .Va FS ) .
    130 This is convenient when working with multi-line records.
    131 .Pp
    132 An input line is normally made up of fields separated by whitespace,
    133 or by the regular expression
    134 .Va FS .
    135 The fields are denoted
    136 .Va $1 , $2 , ... ,
    137 while
    138 .Va $0
    139 refers to the entire line.
    140 If
    141 .Va FS
    142 is null, the input line is split into one field per character.
    143 .Pp
    144 Normally, any number of blanks separate fields.
    145 In order to set the field separator to a single blank, use the
    146 .Fl F
    147 option with a value of
    148 .Sq [\ \&] .
    149 If a field separator of
    150 .Sq t
    151 is specified,
    152 .Nm
    153 treats it as if
    154 .Sq \et
    155 had been specified and uses
    156 .Aq TAB
    157 as the field separator.
    158 In order to use a literal
    159 .Sq t
    160 as the field separator, use the
    161 .Fl F
    162 option with a value of
    163 .Sq [t] .
    164 .Pp
    165 A pattern-action statement has the form
    166 .Pp
    167 .D1 Ar pattern Ic \&{ Ar action Ic \&}
    168 .Pp
    169 A missing
    170 .Ic \&{ Ar action Ic \&}
    171 means print the line;
    172 a missing pattern always matches.
    173 Pattern-action statements are separated by newlines or semicolons.
    174 .Pp
    175 Newlines are permitted after a terminating statement or following a comma
    176 .Pq Sq ,\& ,
    177 an open brace
    178 .Pq Sq { ,
    179 a logical AND
    180 .Pq Sq && ,
    181 a logical OR
    182 .Pq Sq || ,
    183 after the
    184 .Sq do
    185 or
    186 .Sq else
    187 keywords,
    188 or after the closing parenthesis of an
    189 .Sq if ,
    190 .Sq for ,
    191 or
    192 .Sq while
    193 statement.
    194 Additionally, a backslash
    195 .Pq Sq \e
    196 can be used to escape a newline between tokens.
    197 .Pp
    198 An action is a sequence of statements.
    199 A statement can be one of the following:
    200 .Pp
    201 .Bl -tag -width Ds -offset indent -compact
    202 .It Xo Ic if ( Ar expression ) Ar statement
    203 .Op Ic else Ar statement
    204 .Xc
    205 .It Ic while ( Ar expression ) Ar statement
    206 .It Xo Ic for
    207 .No ( Ar expression ; expression ; expression ) statement
    208 .Xc
    209 .It Xo Ic for
    210 .No ( Ar var Ic in Ar array ) statement
    211 .Xc
    212 .It Xo Ic do
    213 .Ar statement Ic while ( Ar expression )
    214 .Xc
    215 .It Ic break
    216 .It Ic continue
    217 .It Xo Ic {
    218 .Op Ar statement ...
    219 .Ic }
    220 .Xc
    221 .It Xo Ar expression
    222 .No # commonly
    223 .Ar var No = Ar expression
    224 .Xc
    225 .It Xo Ic print
    226 .Op Ar expression-list
    227 .Op > Ns Ar expression
    228 .Xc
    229 .It Xo Ic printf Ar format
    230 .Op Ar ... , expression-list
    231 .Op > Ns Ar expression
    232 .Xc
    233 .It Ic return Op Ar expression
    234 .It Xo Ic next
    235 .No # skip remaining patterns on this input line
    236 .Xc
    237 .It Xo Ic nextfile
    238 .No # skip rest of this file, open next, start at top
    239 .Xc
    240 .It Xo Ic delete
    241 .Sm off
    242 .Ar array Ic \&[ Ar expression Ic \&]
    243 .Sm on
    244 .No # delete an array element
    245 .Xc
    246 .It Xo Ic delete Ar array
    247 .No # delete all elements of array
    248 .Xc
    249 .It Xo Ic exit
    250 .Op Ar expression
    251 .No # exit immediately; status is Ar expression
    252 .Xc
    253 .El
    254 .Pp
    255 Statements are terminated by
    256 semicolons, newlines or right braces.
    257 An empty
    258 .Ar expression-list
    259 stands for
    260 .Ar $0 .
    261 String constants are quoted
    262 .Li \&"" ,
    263 with the usual C escapes recognized within
    264 (see
    265 .Xr printf 1
    266 for a complete list of these).
    267 Expressions take on string or numeric values as appropriate,
    268 and are built using the operators
    269 .Ic + \- * / % ^
    270 .Pq exponentiation ,
    271 and concatenation
    272 .Pq indicated by whitespace .
    273 The operators
    274 .Ic \&! ++ \-\- += \-= *= /= %= ^=
    275 .Ic > >= < <= == != ?:
    276 are also available in expressions.
    277 Variables may be scalars, array elements
    278 (denoted
    279 .Li x[i] )
    280 or fields.
    281 Variables are initialized to the null string.
    282 Array subscripts may be any string,
    283 not necessarily numeric;
    284 this allows for a form of associative memory.
    285 Multiple subscripts such as
    286 .Li [i,j,k]
    287 are permitted; the constituents are concatenated,
    288 separated by the value of
    289 .Va SUBSEP
    290 .Pq see the section on variables below .
    291 .Pp
    292 The
    293 .Ic print
    294 statement prints its arguments on the standard output
    295 (or on a file if
    296 .Pf > Ns Ar file
    297 or
    298 .Pf >> Ns Ar file
    299 is present or on a pipe if
    300 .Pf |\ \& Ar cmd
    301 is present), separated by the current output field separator,
    302 and terminated by the output record separator.
    303 .Ar file
    304 and
    305 .Ar cmd
    306 may be literal names or parenthesized expressions;
    307 identical string values in different statements denote
    308 the same open file.
    309 The
    310 .Ic printf
    311 statement formats its expression list according to the format
    312 (see
    313 .Xr printf 1 ) .
    314 .Pp
    315 Patterns are arbitrary Boolean combinations
    316 (with
    317 .Ic "\&! || &&" )
    318 of regular expressions and
    319 relational expressions.
    320 .Nm
    321 supports extended regular expressions
    322 .Pq EREs .
    323 See
    324 .Xr re_format 7
    325 for more information on regular expressions.
    326 Isolated regular expressions
    327 in a pattern apply to the entire line.
    328 Regular expressions may also occur in
    329 relational expressions, using the operators
    330 .Ic ~
    331 and
    332 .Ic !~ .
    333 .Pf / Ns Ar re Ns /
    334 is a constant regular expression;
    335 any string (constant or variable) may be used
    336 as a regular expression, except in the position of an isolated regular expression
    337 in a pattern.
    338 .Pp
    339 A pattern may consist of two patterns separated by a comma;
    340 in this case, the action is performed for all lines
    341 from an occurrence of the first pattern
    342 through an occurrence of the second.
    343 .Pp
    344 A relational expression is one of the following:
    345 .Pp
    346 .Bl -tag -width Ds -offset indent -compact
    347 .It Ar expression matchop regular-expression
    348 .It Ar expression relop expression
    349 .It Ar expression Ic in Ar array-name
    350 .It Xo Ic \&( Ns
    351 .Ar expr , expr , \&... Ns Ic \&) in
    352 .Ar array-name
    353 .Xc
    354 .El
    355 .Pp
    356 where a
    357 .Ar relop
    358 is any of the six relational operators in C, and a
    359 .Ar matchop
    360 is either
    361 .Ic ~
    362 (matches)
    363 or
    364 .Ic !~
    365 (does not match).
    366 A conditional is an arithmetic expression,
    367 a relational expression,
    368 or a Boolean combination
    369 of these.
    370 .Pp
    371 The special patterns
    372 .Ic BEGIN
    373 and
    374 .Ic END
    375 may be used to capture control before the first input line is read
    376 and after the last.
    377 .Ic BEGIN
    378 and
    379 .Ic END
    380 do not combine with other patterns.
    381 .Pp
    382 Variable names with special meanings:
    383 .Pp
    384 .Bl -tag -width "FILENAME " -compact
    385 .It Va ARGC
    386 Argument count, assignable.
    387 .It Va ARGV
    388 Argument array, assignable;
    389 non-null members are taken as filenames.
    390 .It Va CONVFMT
    391 Conversion format when converting numbers
    392 (default
    393 .Qq Li %.6g ) .
    394 .It Va ENVIRON
    395 Array of environment variables; subscripts are names.
    396 .It Va FILENAME
    397 The name of the current input file.
    398 .It Va FNR
    399 Ordinal number of the current record in the current file.
    400 .It Va FS
    401 Regular expression used to separate fields; also settable
    402 by option
    403 .Fl F Ar fs .
    404 .It Va NF
    405 Number of fields in the current record.
    406 .Va $NF
    407 can be used to obtain the value of the last field in the current record.
    408 .It Va NR
    409 Ordinal number of the current record.
    410 .It Va OFMT
    411 Output format for numbers (default
    412 .Qq Li %.6g ) .
    413 .It Va OFS
    414 Output field separator (default blank).
    415 .It Va ORS
    416 Output record separator (default newline).
    417 .It Va RLENGTH
    418 The length of the string matched by the
    419 .Fn match
    420 function.
    421 .It Va RS
    422 Input record separator (default newline).
    423 .It Va RSTART
    424 The starting position of the string matched by the
    425 .Fn match
    426 function.
    427 .It Va SUBSEP
    428 Separates multiple subscripts (default 034).
    429 .El
    430 .Sh FUNCTIONS
    431 The awk language has a variety of built-in functions:
    432 arithmetic, string, input/output, general, and bit-operation.
    433 .Pp
    434 Functions may be defined (at the position of a pattern-action statement)
    435 thusly:
    436 .Pp
    437 .Dl function foo(a, b, c) { ...; return x }
    438 .Pp
    439 Parameters are passed by value if scalar, and by reference if array name;
    440 functions may be called recursively.
    441 Parameters are local to the function; all other variables are global.
    442 Thus local variables may be created by providing excess parameters in
    443 the function definition.
    444 .Ss Arithmetic Functions
    445 .Bl -tag -width "atan2(y, x)"
    446 .It Fn atan2 y x
    447 Return the arctangent of
    448 .Fa y Ns / Ns Fa x
    449 in radians.
    450 .It Fn cos x
    451 Return the cosine of
    452 .Fa x ,
    453 where
    454 .Fa x
    455 is in radians.
    456 .It Fn exp x
    457 Return the exponential of
    458 .Fa x .
    459 .It Fn int x
    460 Return
    461 .Fa x
    462 truncated to an integer value.
    463 .It Fn log x
    464 Return the natural logarithm of
    465 .Fa x .
    466 .It Fn rand
    467 Return a random number,
    468 .Fa n ,
    469 such that
    470 .Sm off
    471 .Pf 0 \*(Le Fa n No \*(Lt 1 .
    472 .Sm on
    473 .It Fn sin x
    474 Return the sine of
    475 .Fa x ,
    476 where
    477 .Fa x
    478 is in radians.
    479 .It Fn sqrt x
    480 Return the square root of
    481 .Fa x .
    482 .It Fn srand expr
    483 Sets seed for
    484 .Fn rand
    485 to
    486 .Fa expr
    487 and returns the previous seed.
    488 If
    489 .Fa expr
    490 is omitted, the time of day is used instead.
    491 .El
    492 .Ss String Functions
    493 .Bl -tag -width "split(s, a, fs)"
    494 .It Fn gsub r t s
    495 The same as
    496 .Fn sub
    497 except that all occurrences of the regular expression are replaced.
    498 .Fn gsub
    499 returns the number of replacements.
    500 .It Fn index s t
    501 The position in
    502 .Fa s
    503 where the string
    504 .Fa t
    505 occurs, or 0 if it does not.
    506 .It Fn length s
    507 The length of
    508 .Fa s
    509 taken as a string,
    510 or of
    511 .Va $0
    512 if no argument is given.
    513 .It Fn match s r
    514 The position in
    515 .Fa s
    516 where the regular expression
    517 .Fa r
    518 occurs, or 0 if it does not.
    519 The variable
    520 .Va RSTART
    521 is set to the starting position of the matched string
    522 .Pq which is the same as the returned value
    523 or zero if no match is found.
    524 The variable
    525 .Va RLENGTH
    526 is set to the length of the matched string,
    527 or \-1 if no match is found.
    528 .It Fn split s a fs
    529 Splits the string
    530 .Fa s
    531 into array elements
    532 .Va a[1] , a[2] , ... , a[n]
    533 and returns
    534 .Va n .
    535 The separation is done with the regular expression
    536 .Ar fs
    537 or with the field separator
    538 .Va FS
    539 if
    540 .Ar fs
    541 is not given.
    542 An empty string as field separator splits the string
    543 into one array element per character.
    544 .It Fn sprintf fmt expr ...
    545 The string resulting from formatting
    546 .Fa expr , ...
    547 according to the
    548 .Xr printf 1
    549 format
    550 .Fa fmt .
    551 .It Fn sub r t s
    552 Substitutes
    553 .Fa t
    554 for the first occurrence of the regular expression
    555 .Fa r
    556 in the string
    557 .Fa s .
    558 If
    559 .Fa s
    560 is not given,
    561 .Va $0
    562 is used.
    563 An ampersand
    564 .Pq Sq &
    565 in
    566 .Fa t
    567 is replaced in string
    568 .Fa s
    569 with regular expression
    570 .Fa r .
    571 A literal ampersand can be specified by preceding it with two backslashes
    572 .Pq Sq \e\e .
    573 A literal backslash can be specified by preceding it with another backslash
    574 .Pq Sq \e\e .
    575 .Fn sub
    576 returns the number of replacements.
    577 .It Fn substr s m n
    578 Return at most the
    579 .Fa n Ns -character
    580 substring of
    581 .Fa s
    582 that begins at position
    583 .Fa m
    584 counted from 1.
    585 If
    586 .Fa n
    587 is omitted, or if
    588 .Fa n
    589 specifies more characters than are left in the string,
    590 the length of the substring is limited by the length of
    591 .Fa s .
    592 .It Fn tolower str
    593 Returns a copy of
    594 .Fa str
    595 with all upper-case characters translated to their
    596 corresponding lower-case equivalents.
    597 .It Fn toupper str
    598 Returns a copy of
    599 .Fa str
    600 with all lower-case characters translated to their
    601 corresponding upper-case equivalents.
    602 .El
    603 .Ss Input/Output and General Functions
    604 .Bl -tag -width "getline [var] < file"
    605 .It Fn close expr
    606 Closes the file or pipe
    607 .Fa expr .
    608 .Fa expr
    609 should match the string that was used to open the file or pipe.
    610 .It Ar cmd | Ic getline Op Va var
    611 Read a record of input from a stream piped from the output of
    612 .Ar cmd .
    613 If
    614 .Va var
    615 is omitted, the variables
    616 .Va $0
    617 and
    618 .Va NF
    619 are set.
    620 Otherwise
    621 .Va var
    622 is set.
    623 If the stream is not open, it is opened.
    624 As long as the stream remains open, subsequent calls
    625 will read subsequent records from the stream.
    626 The stream remains open until explicitly closed with a call to
    627 .Fn close .
    628 .Ic getline
    629 returns 1 for a successful input, 0 for end of file, and \-1 for an error.
    630 .It Fn fflush [expr]
    631 Flushes any buffered output for the file or pipe
    632 .Fa expr ,
    633 or all open files or pipes if
    634 .Fa expr
    635 is omitted.
    636 .Fa expr
    637 should match the string that was used to open the file or pipe.
    638 .It Ic getline
    639 Sets
    640 .Va $0
    641 to the next input record from the current input file.
    642 This form of
    643 .Ic getline
    644 sets the variables
    645 .Va NF ,
    646 .Va NR ,
    647 and
    648 .Va FNR .
    649 .Ic getline
    650 returns 1 for a successful input, 0 for end of file, and \-1 for an error.
    651 .It Ic getline Va var
    652 Sets
    653 .Va $0
    654 to variable
    655 .Va var .
    656 This form of
    657 .Ic getline
    658 sets the variables
    659 .Va NR
    660 and
    661 .Va FNR .
    662 .Ic getline
    663 returns 1 for a successful input, 0 for end of file, and \-1 for an error.
    664 .It Xo
    665 .Ic getline Op Va var
    666 .Pf \ \&< Ar file
    667 .Xc
    668 Sets
    669 .Va $0
    670 to the next record from
    671 .Ar file .
    672 If
    673 .Va var
    674 is omitted, the variables
    675 .Va $0
    676 and
    677 .Va NF
    678 are set.
    679 Otherwise
    680 .Va var
    681 is set.
    682 If
    683 .Ar file
    684 is not open, it is opened.
    685 As long as the stream remains open, subsequent calls will read subsequent
    686 records from
    687 .Ar file .
    688 .Ar file
    689 remains open until explicitly closed with a call to
    690 .Fn close .
    691 .It Fn system cmd
    692 Executes
    693 .Fa cmd
    694 and returns its exit status.
    695 .El
    696 .Ss Bit-Operation Functions
    697 .Bl -tag -width "lshift(a, b)"
    698 .It Fn compl x
    699 Returns the bitwise complement of integer argument x.
    700 .It Fn and x y
    701 Performs a bitwise AND on integer arguments x and y.
    702 .It Fn or x y
    703 Performs a bitwise OR on integer arguments x and y.
    704 .It Fn xor x y
    705 Performs a bitwise Exclusive-OR on integer arguments x and y.
    706 .It Fn lshift x n
    707 Returns integer argument x shifted by n bits to the left.
    708 .It Fn rshift x n
    709 Returns integer argument x shifted by n bits to the right.
    710 .El
    711 .Sh EXIT STATUS
    712 .Ex -std awk
    713 .Pp
    714 But note that the
    715 .Ic exit
    716 expression can modify the exit status.
    717 .Sh EXAMPLES
    718 Print lines longer than 72 characters:
    719 .Pp
    720 .Dl length($0) > 72
    721 .Pp
    722 Print first two fields in opposite order:
    723 .Pp
    724 .Dl { print $2, $1 }
    725 .Pp
    726 Same, with input fields separated by comma and/or blanks and tabs:
    727 .Bd -literal -offset indent
    728 BEGIN { FS = ",[ \et]*|[ \et]+" }
    729       { print $2, $1 }
    730 .Ed
    731 .Pp
    732 Add up first column, print sum and average:
    733 .Bd -literal -offset indent
    734 { s += $1 }
    735 END { print "sum is", s, " average is", s/NR }
    736 .Ed
    737 .Pp
    738 Print all lines between start/stop pairs:
    739 .Pp
    740 .Dl /start/, /stop/
    741 .Pp
    742 Simulate echo(1):
    743 .Bd -literal -offset indent
    744 BEGIN { # Simulate echo(1)
    745         for (i = 1; i < ARGC; i++) printf "%s ", ARGV[i]
    746         printf "\en"
    747         exit }
    748 .Ed
    749 .Pp
    750 Print an error message to standard error:
    751 .Bd -literal -offset indent
    752 { print "error!" > "/dev/stderr" }
    753 .Ed
    754 .Sh SEE ALSO
    755 .Xr lex 1 ,
    756 .Xr printf 1 ,
    757 .Xr sed 1 ,
    758 .Xr re_format 7 ,
    759 .Xr script 7
    760 .Rs
    761 .%A A. V. Aho
    762 .%A B. W. Kernighan
    763 .%A P. J. Weinberger
    764 .%T The AWK Programming Language
    765 .%I Addison-Wesley
    766 .%D 1988
    767 .%O ISBN 0-201-07981-X
    768 .Re
    769 .Sh STANDARDS
    770 The
    771 .Nm
    772 utility is compliant with the
    773 .St -p1003.1-2008
    774 specification,
    775 except
    776 .Nm
    777 does not support {n,m} pattern matching.
    778 .Pp
    779 The flags
    780 .Op Fl \&dV
    781 and
    782 .Op Fl safe ,
    783 as well as the commands
    784 .Cm fflush , compl , and , or ,
    785 .Cm xor , lshift , rshift ,
    786 are extensions to that specification.
    787 .Sh HISTORY
    788 An
    789 .Nm
    790 utility appeared in
    791 .At v7 .
    792 .Sh BUGS
    793 There are no explicit conversions between numbers and strings.
    794 To force an expression to be treated as a number add 0 to it;
    795 to force it to be treated as a string concatenate
    796 .Li \&""
    797 to it.
    798 .Pp
    799 The scope rules for variables in functions are a botch;
    800 the syntax is worse.