NAME
awk - pattern-directed scanning and processing language
SYNOPSIS
awk [-Ffs ] [-vvar=value ] [ program ⏐ -fprog®le ... ] [ ®le ... ]
DESCRIPTION
awk scans each input ®le for lines that match any of a set of patterns speci®ed literally in program or in one or more ®les speci®ed as -fprog®le. With each pattern there can be an associated action that is to be performed when a line in a ®le matches the pattern. Each line is matched against the pattern portion of every pattern-action statement, and the associated action is performed for each matched pattern. The ®le name - means the standard input. Any ®le of the form var=value is treated as an assignment, not a ®lename. An assignment is evaluated at the time it would have been opened if it were a ®lename, unless the -voption is used.
An input line is made up of ®elds separated by white space, or by regular expression FS. The ®elds are denoted $1, $2, ...; $0 refers to the entire line.
Options
awk recognizes the following options and arguments:
-F fs | Specify regular expression used to separate ®elds. The default is to recognize space |
| and tab characters, and to discard leading spaces and tabs. If the -Foption is used, |
| leading input ®eld separators are no longer discarded. |
-fprogfile | Specify an awk program ®le. Up to 100 program ®les can be speci®ed. The pattern- |
| action statements in these ®les are executed in the same order as the ®les were |
| speci®ed. |
-vvar=value Cause var=value assignment to occur before the BEGIN action (if it exists) is exe- cuted.
Statements
A pattern-action statement has the form:
pattern { action }
A missing { action } means print the line; a missing pattern always matches. Pattern-action statements are separated by new-lines or semicolons.
An action is a sequence of statements. A statement can be one of the following:
if( expression ) statement [ else statement ] while( expression) statement
for( expression ; expression ; expression) statement
for( var in array ) statement | |
do statement | while( expression ) | |
break | | |
continue | | |
{ [ statement | ... ] } | |
expression | | # commonly var = expression |
print [ expression-list ] [ > expression ] |
printf format [, expression-list ] | [ > expression ] |
return [ expression ] | |
next | [ expression ] | # skip remaining patterns on this input line. |
delete array | # delete an array element. |
exit [ expression ] | # exit immediately; status is expression. |
Statements are terminated by semicolons, newlines or right braces. An empty expression-liststands for $0. String constants are quoted (" "), with the usual C escapes recognized within. Expressions take on string or numeric values as appropriate, and are built using the operators +, -, *, /, %, Ã (exponentiation), and concatenation (indicated by a blank). The operators ++, - -, +=, -=, *=, /=, %=, Ã=, **=, >, >=, <, <=, ==, !=, and ?: are also available in expressions. Variables can be scalars, array elements (denoted x[i]) or ®elds. Variables are initialized to the null string. Array subscripts can be any string, not necessarily numeric (this allows for a form of associative memory). Multiple subscripts such as [ i,j,k ] are permitted. The constituents are concatenated, separated by the value of SUBSEP.
Section 1−34 | − 1 − | HP-UX Release 11i: December 2000 |
