awk(1) User Commands awk(1)NAMEawk - pattern scanning and processing language
SYNOPSIS
/usr/bin/awk [-f progfile] [-Fc] [' prog '] [parameters]
[filename]...
/usr/xpg4/bin/awk [-FcERE] [-v assignment]... 'program' -f progfile...
[argument]...
DESCRIPTION
The /usr/xpg4/bin/awk utility is described on the nawk(1) manual page.
The /usr/bin/awk utility scans each input filename for lines that match
any of a set of patterns specified in prog. The prog string must be
enclosed in single quotes (a´) to protect it from the shell. For each
pattern in prog there can be an associated action performed when a line
of a filename matches the pattern. The set of pattern-action statements
can appear literally as prog or in a file specified with the -f prog‐
file option. Input files are read in order; if there are no files, the
standard input is read. The file name '−' means the standard input.
OPTIONS
The following options are supported:
-f progfile awk uses the set of patterns it reads from progfile.
-Fc Uses the character c as the field separator (FS) charac‐
ter. See the discussion of FS below.
USAGE
Input Lines
Each input line is matched against the pattern portion of every pat‐
tern-action statement; the associated action is performed for each
matched pattern. Any filename of the form var=value is treated as an
assignment, not a filename, and is executed at the time it would have
been opened if it were a filename. Variables assigned in this manner
are not available inside a BEGIN rule, and are assigned after previ‐
ously specified files have been read.
An input line is normally made up of fields separated by white spaces.
(This default can be changed by using the FS built-in variable or the
-Fc option.) The default is to ignore leading blanks and to separate
fields by blanks and/or tab characters. However, if FS is assigned a
value that does not include any of the white spaces, then leading
blanks are not ignored. The fields are denoted $1, $2, ...; $0 refers
to the entire line.
Pattern-action Statements
A pattern-action statement has the form:
pattern { action }
Either pattern or action can be omitted. If there is no action, the
matching line is printed. If there is no pattern, the action is per‐
formed on every input line. Pattern-action statements are separated by
newlines or semicolons.
Patterns are arbitrary Boolean combinations ( !, ||, &&, and parenthe‐
ses) of relational expressions and regular expressions. A relational
expression is one of the following:
expression relop expression
expression matchop regular_expression
where a relop is any of the six relational operators in C, and a
matchop is either ~ (contains) or !~ (does not contain). An expression
is an arithmetic expression, a relational expression, the special
expression
var in array
or a Boolean combination of these.
Regular expressions are as in egrep(1). In patterns they must be sur‐
rounded by slashes. Isolated regular expressions in a pattern apply to
the entire line. Regular expressions can also occur in relational
expressions. A pattern can consist of two patterns separated by a
comma; in this case, the action is performed for all lines between the
occurrence of the first pattern to the occurrence of the second pat‐
tern.
The special patterns BEGIN and END can be used to capture control
before the first input line has been read and after the last input line
has been read respectively. These keywords do not combine with any
other patterns.
Built-in Variables
Built-in variables include:
FILENAME name of the current input file
FS input field separator regular expression (default blank and
tab)
NF number of fields in the current record
NR ordinal number of the current record
OFMT output format for numbers (default %.6g)
OFS output field separator (default blank)
ORS output record separator (default new-line)
RS input record separator (default new-line)
An action is a sequence of statements. A statement can be one of the
following:
if ( expression ) statement [ else statement]
while ( expression ) statement
do statement while ( expression )
for ( expression ; expression ; expression ) statement
for ( var in array ) statement
break
continue
{ [ statement ] ... }
expression # commonly variable = expression
print [ expression-list ] [ >expression ]
printf format [ ,expression-list ] [ >expression ]
next # skip remaining patterns on this input line
exit [expr] # skip the rest of the input; exit status is expr
Statements are terminated by semicolons, newlines, or right braces. An
empty expression-list stands for the whole input line. Expressions take
on string or numeric values as appropriate, and are built using the
operators +, −, *, /, %, ^ and concatenation (indicated by a blank).
The operators ++, −−, +=, −=, *=, /=, %=, ^=, >, >=, <, <=, ==, !=, and
?: are also available in expressions. Variables can be scalars, array
elements (denoted x[i]), or fields. Variables are initialized to the
null string or zero. Array subscripts can be any string, not necessar‐
ily numeric; this allows for a form of associative memory. String con‐
stants are quoted (""), with the usual C escapes recognized within.
The print statement prints its arguments on the standard output, or on
a file if >expression is present, or on a pipe if '|cmd' is present.
The output resulted from the print statement is terminated by the out‐
put record separator with each argument separated by the current output
field separator. The printf statement formats its expression list
according to the format (see printf(3C)).
Built-in Functions
The arithmetic functions are as follows:
cos(x) Return cosine of x, where x is in radians. (In
/usr/xpg4/bin/awk only. See nawk(1).)
sin(x) Return sine of x, where x is in radians. (In
/usr/xpg4/bin/awk only. See nawk(1).)
exp(x) Return the exponential function of x.
log(x) Return the natural logarithm of x.
sqrt(x) Return the square root of x.
int(x) Truncate its argument to an integer. It is truncated toward
0 when x > 0.
The string functions are as follows:
index(s , t)
Return the position in string s where string t first occurs, or 0
if it does not occur at all.
int(s)
truncates s to an integer value. If s is not specified, $0 is used.
length(s)
Return the length of its argument taken as a string, or of the
whole line if there is no argument.
split(s, a, fs)
Split the string s into array elements a[1], a[2], ... a[n], and
returns n. The separation is done with the regular expression fs or
with the field separator FS if fs is not given.
sprintf(fmt, expr, expr,...)
Format the expressions according to the printf(3C) format given by
fmt and returns the resulting string.
substr(s, m, n)
returns the n-character substring of s that begins at position m.
The input/output function is as follows:
getline Set $0 to the next input record from the current input file.
getline returns 1 for successful input, 0 for end of file,
and −1 for an error.
Large File Behavior
See largefile(5) for the description of the behavior of awk when
encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).
EXAMPLES
Example 1 Printing Lines Longer Than 72 Characters
The following example is an awk script that can be executed by an awk-f examplescript style command. It prints lines longer than seventy two
characters:
length > 72
Example 2 Printing Fields in Opposite Order
The following example is an awk script that can be executed by an awk-f examplescript style command. It prints the first two fields in oppo‐
site order:
{ print $2, $1 }
Example 3 Printing Fields in Opposite Order with the Input Fields Sepa‐
rated
The following example is an awk script that can be executed by an awk-f examplescript style command. It prints the first two input fields in
opposite order, separated by a comma, blanks or tabs:
BEGIN { FS = ",[ \t]*|[ \t]+" }
{ print $2, $1 }
Example 4 Adding Up the First Column, Printing the Sum and Average
The following example is an awk script that can be executed by an awk-f examplescript style command. It adds up the first column, and
prints the sum and average:
{ s += $1 }
END { print "sum is", s, " average is", s/NR }
Example 5 Printing Fields in Reverse Order
The following example is an awk script that can be executed by an awk-f examplescript style command. It prints fields in reverse order:
{ for (i = NF; i > 0; −−i) print $i }
Example 6 Printing All lines Between start/stop Pairs
The following example is an awk script that can be executed by an awk-f examplescript style command. It prints all lines between start/stop
pairs.
/start/, /stop/
Example 7 Printing All Lines Whose First Field is Different from the
Previous One
The following example is an awk script that can be executed by an awk-f examplescript style command. It prints all lines whose first field
is different from the previous one.
$1 != prev { print; prev = $1 }
Example 8 Printing a File and Filling in Page numbers
The following example is an awk script that can be executed by an awk-f examplescript style command. It prints a file and fills in page num‐
bers starting at 5:
/Page/ { $2 = n++; }
{ print }
Example 9 Printing a File and Numbering Its Pages
Assuming this program is in a file named prog, the following example
prints the file input numbering its pages starting at 5:
example% awk-f prog n=5 input
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables
that affect the execution of awk: LANG, LC_ALL, LC_COLLATE, LC_CTYPE,
LC_MESSAGES, NLSPATH, and PATH.
LC_NUMERIC Determine the radix character used when interpreting
numeric input, performing conversions between numeric and
string values and formatting numeric output. Regardless
of locale, the period character (the decimal-point char‐
acter of the POSIX locale) is the decimal-point character
recognized in processing awk programs (including assign‐
ments in command-line arguments).
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
/usr/bin/awk
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Availability │SUNWesu │
├─────────────────────────────┼─────────────────────────────┤
│CSI │Not Enabled │
└─────────────────────────────┴─────────────────────────────┘
/usr/xpg4/bin/awk
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Availability │SUNWxcu4 │
├─────────────────────────────┼─────────────────────────────┤
│CSI │Enabled │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Committed │
├─────────────────────────────┼─────────────────────────────┤
│Standard │See standards(5). │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOegrep(1), grep(1), nawk(1), sed(1), printf(3C), attributes(5), envi‐
ron(5), largefile(5), standards(5)NOTES
Input white space is not preserved on output if fields are involved.
There are no explicit conversions between numbers and strings. To force
an expression to be treated as a number, add 0 to it. To force an
expression to be treated as a string, concatenate the null string ("")
to it.
SunOS 5.10 4 May 2010 awk(1)