awk [ -F fs ]
[ -v var=value ]
[ prog | -f progFile … ]
[ inputFile [ var=value] … ]
Scans each inputFile for lines that match any of a set of patterns
in prog or -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 statement;
the associated action is performed for each matched pattern.
Use - instead of inputFile to process input from stdin.
Constructs of the form var=value
are treated as an assignment, and are executed at the
time it would have been opened if it were a inputFile
-v var=value is an assignment done before prog is executed;
any number of -v options may be used.
-F fs 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.
If FS is null, the input line is split
into one character per field.
A pattern-action statement has the form
pattern{ action }
pattern matches all lines.
{ action } prints the line.
action statements are separated by newlines or semi-colons.
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
nextfile # skip rest of this file, open next, start at top
delete array[ expression ]# delete an array element
delete array # delete all elements of array
exit [ expression ] # exit immediately; status is expression
Statements are terminated by semicolons, newlines or right braces.
An empty expression-list implies $0, that is the entire input line.
String constants are quoted " ", with the usual C escapes recognized within.
Expressions take on string or numeric values as appropriate, and are built with operators + -
* / % ^ (exponentiation), and concatenation (indicated by white space).
operators: ! ++ -- += -= *= /= %= ^= > > < < == != ?: .
Variables may be scalars, array elements (denoted x[i]) or fields, are initialized to the null.
Array subscripts may be strings.
Multiple subscripts such as [i,j,k] are permitted; the constituents are concatenated, separated
by the value of SUBSEP.
print arguments output to standard output separated by Output Field Separator (default tab),\n(newLine)). printf formats its expression list Add new lines with \n # The value should be converted to an alternate form. x and X a non-zero result has the string '0x' (or '0X' for X conversions) prepended
to it.
a, A, e, E, f, F, g, and G , the result will always contain a decimal
point, even if no digits follow it (normally, a decimal point appears in the results of those
conversions only if a digit follows).
g and G trailing zeros are not removed from the result as they would otherwise be.<
o (octal) the first character of the output string is made zero (by prefixing a 0 if it was not zero already).
0 The value should be zero padded. For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, the converted value is padded on the left with zeros rather than blanks. If the 0 and
- flags both appear, the 0 flag is ignored. If a precision is given with a numeric conversion
(d, i, o, u, x, and X), the 0 flag is ignored. For other conversions, the behavior is undefined.
- The converted value is to be left adjusted on the field boundary. (The default is right jus-
tification.) Except for n conversions, the converted value is padded on the right with blanks,
rather than on the left with blanks or zeros. A - overrides a 0 if both are given.
+A sign (+ or -) should always be placed before a number produced by a signed conversion. By
default a sign is used only for negative numbers. A + overrides a space if both are used.
The flag characters above are defined in the C standard. The SUSv2 adds:
' For decimal conversion (i, d, u, f, F, g, G) the output is to be grouped with thousands'
grouping characters if the locale information indicates any. Note that many versions of
gcc(1) cannot parse this option and will issue a warning. SUSv2 does not include %'F.
glibc 2.2 adds:I For decimal integer conversion (i, d, u) the output uses the locale's alternative output digits, if any. For example, this will give Arabic-Indic digits in the Persian ('fa_IR') locale.
example: printf "%6d %s", NR, $0
close(expr) closes the file or pipe expr.
fflush(expr) flushes any buffered output for the file or pipe expr.
exp, log, sqrt, sin, cos, and atan2 .
length the length of its argument taken as a string, or of $0 if no argument.
rand random number on (0,1) ; srand sets seed for rand and returns the previous seed.
int truncates to an integer value
substr(string,m,n) the nth-character substring of string that begins at position m counted from 1.
index(s,t) the position in s where the string t occurs, or 0 if it does not.
match(s,r) the position in s where the regular expression r occurs, or 0 if it does not.
RSTART and RLENGTH are set to the position and length of the matched string.
split(string,array[,fs]) splits string
into array elements array[1], array[2], … array[n], and returns ni. The separation is done with the regular expression fs
or with the field separator FS if fs is not given.
splits the string into 1 array element per character.
sub(regex,repl[,string]) substitutes repl for the first occurrence of the regular expression
regex in string.
$0 is the default for string .
gsub same as sub except that all occurrences of the regular expression are replaced; sub and gsub return the number of replacements.
sprintf(fmt, expr, ... ) the string resulting from formatting expr ... according to the printf(3) format fmt
system(cmd) executes cmd and returns its exit status
tolower(str) returns a copy of str with all upper-case characters translated to their corresponding lower-case equivalents.
toupper(str) returns a copy of str with all lower-case characters translated to their corresponding upper-case equivalents.
getline sets $0 to the next input record from the current input file;
getline < file sets $0 to the next record from file.
getline x sets variable x instead. Finally, cmd | getline pipes the
output of cmd into getline; each call of getline returns the next line
of output from cmd. In all cases, getline returns 1 for a successful
input, 0 for end of file, and -1 for an error.
Patterns are arbitrary Boolean combinations (with ! || && of regular
expressions and relational expressions. Regular expressions are as in
egrep; see grep.
Isolated regular expressions in a pattern apply to the entire line.
Regular expressions may also occur in relational expressions, using the operators ~ and !~.
/re/ is a constant regular expression; any string (constant or variable) may be used as
a regular expression, except in the position of an isolated regular expression in a pattern.
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 < <= == >= > ! and
matchop is either ~ (matches) or !~ (does not match).
A conditional is an arithmetic expression, a relational expression, or a Boolean combination 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).
CONVFMT conversion format used when converting numbers (default %.6g )
FS regular expression used to separate fields; also settable by option -Ffs.
NF number of fields in the current record
NR ordinal number of the current record
FNR ordinal number of the current record in the current file
FILENAME the name of the current input file
RS input record separator (default newline)
OFS output field separator (default blank)
ORS output record separator (default newline)
OFMT output format for numbers (default %.6g)
SUBSEP separates multiple subscripts (default 034)
ARGC argument count, assignable
ARGV argument array, assignable; non-null members are taken as filenames
ENVIRON array of environment variables; subscripts are names.
Functions may be defined (at the position of a pattern-action statement) thus:
function foo(a, b, c) { ...; return x }
Parameters are passed by value if scalar and by reference if array
name; functions may be called recursively.
awk "{ if( length > 80 ) print NR,substr(\$0,1,30),substr(\$0,80,100 ) }" system.log
|
$ and " from the shell intrepertation.2093 Nov 26 23:59:22 2009 System Lo S:71.250.0.12 68.237.161.12 ,GTW:173.54.41.1,Subnet:255.255.255.0 (WAN MoCA) 2095 Nov 27 04:00:11 2009 System Lo DNS:192.168.1.1,GTW:192.168.1.1,Subnet:255.255.255.0 (MoCA) 2097 Nov 27 04:59:28 2009 System Lo S:71.250.0.12 68.237.161.12 ,GTW:173.54.41.1,Subnet:255.255.255.0 (WAN MoCA) 2099 Nov 27 06:20:12 2009 System Lo S:192.168.1.1,GTW:192.168.1.1,Subnet:255.255.255.0 (Ethernet) 2101 Nov 27 06:53:01 2009 System Lo S:192.168.1.1,GTW:192.168.1.1,Subnet:255.255.255.0 (Wireless) 2103 Nov 27 06:59:30 2009 System Lo S:71.250.0.12 68.237.161.12 ,GTW:173.54.41.1,Subnet:255.255.255.0 (WAN MoCA) 2105 Nov 27 07:05:06 2009 System Lo S:192.168.1.1,GTW:192.168.1.1,Subnet:255.255.255.0 (Ethernet) 2107 Dec 14 19:00:04 2007 System Lo S:192.168.1.1,GTW:192.168.1.1,Subnet:255.255.255.0 (Wireless)
Print first two fields in opposite order.
{ print $2, $1 }
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 all lines between start/stop pairs.
/start/, /stop/
BEGIN { # Simulate echo(1)
for (i = 1; i < ARGC; i++) printf "%s ", ARGV[i]
printf "\n"
exit }
LC_ALL=en_US.UTF-8
Causes the Awk printf to output numbers GT 999 with commas when using ' in the format string.
>cat awkTest.sh
awk -f awkTest.awk
LC_ALL=en_US.UTF-8 awk -f awkTest.awk
> cat awkTest.awk
{ printf " %'d ", i1234567 }
> ./awkTest.sh
1234567
1,234,567
SEE lex(1), sed(1)
BUGS
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 scope rules for variables in functions are a botch; the syntax is worse.