SYNOPSIS
nawk [-f progfile | 'prog'] [-Ffieldsep] [-v var=value] [file . . .]
DESCRIPTION
Nawk scans each input file for lines that match any of a set of pat-
terns specified literally in prog or in one or more files specified as
-f progfile. With each pattern there can be an associated action that
will be performed when a line of a file matches the pattern. Each line
is matched against the pattern portion of every pattern-action state-
ment; 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, and is executed at the
time it would have been opened if it were a filename
(/usr/5bin/s42/awk, /usr/5bin/posix/awk, and /usr/5bin/posix2001/awk
only). The option -v followed by var=value is an assignment to be done
before prog is executed; any number of -v options may be present. The
-F fs option defines the input field separator to be the regular
expression fs.
An input line is normally made up of fields separated by white space,
or by regular expression FS. The fields are denoted $1, $2, ..., while
$0 refers to the entire line.
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 newlines or semi-
colons.
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]
next # skip remaining patterns on this input line
delete array[subscript] # delete an array element
exit [expr] # exit immediately; status is expr
return [expr]
Statements are terminated by semicolons, newlines or right braces. An
empty expression-list stands for $0. String constants are quoted " ",
output record separator. file and cmd may be literal names or paren-
thesized expressions; identical string values in different statements
denote the same open file. The printf statement formats its expression
list according to the format (see printf(3)). The built-in function
close(expr) closes the file or pipe expr.
The mathematical functions exp, log, sqrt, sin, cos, and atan2 are
built in. Other built-in functions:
gsub same as sub except that all occurrences of the regular expres-
sion are replaced; sub and gsub return the number of replace-
ments.
index(s, t)
the position in s where the string t occurs, or 0 if it does
not.
int truncates to an integer value
length the length of its argument taken as a string, or of $0 if no
argument.
match(s, r)
the position in s where the regular expression r occurs, or 0 if
it does not. The variables RSTART and RLENGTH are set to the
position and length of the matched string.
rand random number on (0,1)
split(s, a, fs)
splits the string s into array elements a[1], a[2], ..., a[n],
and returns n. The separation is done with the regular expres-
sion fs or with the field separator FS if fs is not given.
sprintf(fmt, expr, ...)
the string resulting from formatting expr ... according to the
printf(3) format fmt
srand sets seed for rand and returns the previous seed.
sub(r, t, s)
substitutes t for the first occurrence of the regular expression
r in the string s. If s is not given, $0 is used.
substr(s, m, n)
the n-character substring of s that begins at position m counted
from 1.
system(cmd)
executes cmd and returns its exit status
tolower(str)
Additional functions may be defined (at the position of a pattern-
action statement) thus:
function foo(a, b, c) { ...; return x }
or:
func foo(a, b, c) { ...; return x }
Parameters are passed by value if scalar and by reference if array
name; functions may be called recursively. Parameters are local to the
function; all other variables are global. Thus local variables may be
created by providing excess parameters in the function definition.
Patterns are arbitrary Boolean combinations (with ! || &&) of regular
expressions and relational expressions. Regular expressions are full
regular expressions with /usr/5bin/nawk and extended regular expres-
sions with /usr/5bin/s42/awk, /usr/5bin/posix/awk, and
/usr/5bin/posix2001/awk; both are as described in egrep(1). Isolated
regular expressions in a pattern apply to the entire line. Regular
expressions may also occur in relational expressions, using the opera-
tors ~ and !~. /re/ is a constant regular expression; any string (con-
stant or variable) may be used as a regular expression, except in the
position of an isolated regular expression in a pattern. For
/usr/5bin/posix2001/awk, regular expressions may be part of arithmetic
expressions.
A pattern may consist of two patterns separated by a comma; in this
case, the action is performed for all lines from an occurrence of the
first pattern though an occurrence of the second.
A relational expression is one of the following:
expression matchop regular-expression
expression relop expression
expression in array-name
(expr,expr,...) in array-name
where a relop is any of the six relational operators in C, and a
matchop is either ~ (matches) or !~ (does not match). A conditional is
an arithmetic expression, a relational expression, or a Boolean combi-
nation of these.
The special patterns BEGIN and END may be used to capture control
before the first input line is read and after the last. BEGIN and END
do not combine with other patterns.
Variable names with special meanings:
ARGC argument count, assignable
ARGV argument array, assignable; non-null members are taken as
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 newline)
RS input record separator (default newline)
SUBSEP separates multiple subscripts (default 034)
EXAMPLES
length($0) > 72
Print lines longer than 72 characters.
{ print $2, $1 }
Print first two fields in opposite order.
BEGIN { FS = ",[ \t]*|[ \t]+" }
{ print $2, $1 }
Same, with input fields separated by comma and/or blanks and
tabs.
{ s += $1 }
END { print "sum is", s, " average is", s/NR }
Add up first column, print sum and average.
/start/, /stop/
Print all lines between start/stop pairs.
BEGIN { # Simulate echo(1)
for (i = 1; i < ARGC; i++) printf "%s ", ARGV[i]
printf "\n"
exit }
ENVIRONMENT VARIABLES
LANG, LC_ALL
See locale(7).
LC_COLLATE
Affects the collation order for range expressions, equivalence
classes, and collation symbols in regular expressions as well as
string comparison.
LC_CTYPE
Determines the mapping of bytes to characters, the availability
and composition of character classes in regular expressions, and
the case mapping for the toupper() and tolower() functions.
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 concatenate "" to it.
The LC_COLLATE variable has currently no effect in regular expressions.
Ranges in bracket expressions are ordered as byte values in single-byte
locales and as wide character values in multibyte locales; equivalence
classes match the given character only, and multi-character collating
elements are not available.
Heirloom Toolchest 2/6/05 NAWK(1)
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