Command Reference Guide
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STANDARD Printed by: Nora Chuang [nchuang] STANDARD
/build/1111/BRICK/man1/!!!intro.1
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a
awk(1) awk(1)
NAME
awk - pattern-directed scanning and processing language
SYNOPSIS
awk [-Ffs ][-v var=value][program -f progfile ...] [file ...]
DESCRIPTION
awk scans each input file for lines that match any of a set of patterns specified literally in program or in
one or more files specified as -f progfile. With each pattern there can be an associated action that is to be
performed when a line in a file 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 file
name - means the standard input. Any file of the form var=value is treated as an assignment, not a
filename. An assignment is evaluated at the time it would have been opened if it were a filename, unless
the -v option is used.
An input line is made up of fields separated by white space, or by regular expression FS. The fields 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 fields. The default is to recognize space
and tab characters, and to discard leading spaces and tabs. If the -F option is used,
leading input field separators are no longer discarded.
-f progfile Specify an awk program file. Up to 100 program files can be specified. The pattern-
action statements in these files are executed in the same order as the files were
specified.
-v var=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 # skip remaining patterns on this input line.
delete array [expression] # delete an array element.
exit [expression] # exit immediately; status is expression.
Statements are terminated by semicolons, newlines or right braces. An empty expression-list stands 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 +, -, *, /, %, ˆ (exponentiation),
and concatenation (indicated by a blank). The operators ++, --, +=, -=, *=, /=, %=
, ˆ=, **=, >, >=, <,
<=, ==, !=, and ?: are also available in expressions. Variables can be scalars, array elements (denoted
x[i]) or fields. Variables are initialized to the null string. Array subscripts can be any string, not neces-
sarily 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
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