awk(1)
NAME
awk - pattern scanning and processing language
SYNOPSIS
/usr/bin/awk [-f progfile] [-F c] [ ' prog '] [parameters]
[filename...]
/usr/xpg4/bin/awk [-F ERE] [-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 ( ') to pro-
tect it from the shell. For each pattern in prog there may
be an associated action performed when a line of a filename
matches the pattern. The set of pattern-action statements
may appear literally as prog or in a file specified with the
-f progfile 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) char-
acter. See the discussion of FS below.
USAGE
Input Lines
Each input line is matched against the pattern portion of
every pattern-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 avail-
able inside a BEGIN rule, and are assigned after previously
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 may be omitted. If there is no
action, the matching line is printed. If there is no pat-
tern, the action is performed on every input line. Pattern-
action statements are separated by newlines or semicolons.
Patterns are arbitrary Boolean combinations ( !, ||, &&, and
parentheses) of relational expressions and regular expres-
sions. 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 con-
tain). An expression is an arithmetic expression, a rela-
tional 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 surrounded by slashes. Isolated regular expressions
in a pattern apply to the entire line. Regular expressions
may also occur in relational expressions. A pattern may con-
sist 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 pattern.
The special patterns BEGIN and END may be used to capture
control before the first input line has been read and after
the last input line has been read respectively. These key-
words 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 may 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 may be scalars,
array elements (denoted x[i]), or fields. Variables are ini-
tialized to the null string or zero. Array subscripts may be
any string, not necessarily numeric; this allows for a form
of associative memory. String constants 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 output record separator with
each argument separated by the current output field separa-
tor. 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 will be trun-
cated 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 speci-
fied, $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
example% length > 72
Example 2: Printing first two fields in opposite order
example% { print $2, $1 }
Example 3: Same, with input fields separated by comma and/or
blanks and tabs
example% BEGIN { FS = ",[ \t]*|[ \t]+" }
{ print $2, $1 }
Example 4: Adding up first column, print sum and average
example% { s += $1 }
END { print "sum is", s, " average is", s/NR }
Example 5: Printing fields in reverse order
example% { for (i = NF; i > 0; --i) print $i }
Example 6: Printing all lines between start/stop pairs
example% /start/, /stop/
Example 7: Printing all lines whose first field is different
from the previous one
example% $1 != prev { print; prev = $1 }
Example 8: Printing a file, filling in page numbers starting
at 5
example% /Page/ { $2 = n++; }
{ print }
Example 9: Printing a file and numbering its pages, starting
at 5
Assuming this program is in a file named prog, the following
command line 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 character of the POSIX locale) is the
decimal-point character recognized in processing awk
programs (including assignments in command-line argu-
ments).
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
/usr/bin/awk
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWesu |
|_____________________________|_____________________________|
| CSI | Enabled |
|_____________________________|_____________________________|
/usr/xpg4/bin/awk
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWxcu4 |
|_____________________________|_____________________________|
| CSI | Enabled |
|_____________________________|_____________________________|
| Interface Stability | Standard |
|_____________________________|_____________________________|
SEE ALSO
egrep(1), grep(1), nawk(1), sed(1), printf(3C), attri-
butes(5), environ(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.
Man(1) output converted with
man2html