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User Commands awk(1)
NAME
awk - pattern scanning and processing language
SYNOPSIS
/usr/bin/awk [ -f progfile ] [ -Fc ] [ '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 protect
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
-f progfile awk uses the set of patterns it reads from
progfile.
-Fc Use the character c as the field separator
(FS) character. 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
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.
SunOS 5.6 Last change: 18 Mar 1997 1
User Commands awk(1)
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 semi-
colons.
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
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 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
SunOS 5.6 Last change: 18 Mar 1997 2
User Commands awk(1)
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 opera-
tors ++, --, +=, -=, *=, /=, %=, ^=, >, >=, <, <=, ==, !=,
and ?: are also available in expressions. Variables may be
scalars, array elements (denoted x[i]), or fields. Vari-
ables are initialized 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(3S)).
Built-in Functions
The arithmetic functions are as follows:
cos(x) Return cosine of x, where x is in
SunOS 5.6 Last change: 18 Mar 1997 3
User Commands awk(1)
radians.
sin(x) Return sine of x, where x is in radians.
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 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.
match(s, re) Return the position in string s where
the regular expression re occurs, or 0
if it does not occur at all.
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 separa-
tor FS if fs is not given.
sprintf(fmt, expr, expr,...)
Format the expressions according to the
printf(3S) 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.
SunOS 5.6 Last change: 18 Mar 1997 4
User Commands awk(1)
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
Print lines longer than 72 characters:
length > 72
Print first two fields in opposite order:
{ print $2, $1 }
Same, with input fields separated by comma and/or blanks and
tabs:
BEGIN { FS = ",[ \t]*|[ \t]+" }
{ print $2, $1 }
Add up first column, print sum and average:
{ s += $1 }
END { print "sum is", s, " average is", s/NR }
Print fields in reverse order:
{ for (i = NF; i > 0; --i) print $i }
Print all lines between start/stop pairs:
/start/, /stop/
Print all lines whose first field is different from previous
one:
$1 != prev { print; prev = $1 }
Print a file, filling in page numbers starting at 5:
/Page/ { $2 = n++; }
{ print }
Assuming this program is in a file named prog, the following
command line prints the file input numbering its pages
starting at 5: awk -f prog n=5 input.
ENVIRONMENT
See environ(5) for descriptions of the following environment
variables that affect the execution of awk: LC_CTYPE and
LC_MESSAGES.
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User Commands awk(1)
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 |
|_______________|_________________|
SEE ALSO
egrep(1), grep(1), nawk(1), sed(1), printf(3S), attri-
butes(5), environ(5), largefile(5), xpg4(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 it to be treated as a string concaten-
ate the null string ("") to it.
SunOS 5.6 Last change: 18 Mar 1997 6
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