AWK(1) COMMAND REFERENCE AWK(1)
NAME
awk - pattern scanning and processing language
SYNOPSIS
awk [ -Fc ] [ prog ] [ filename... ]
DESCRIPTION
Awk scans each input filename for lines that match any of a
set of patterns specified in prog. With each pattern in
prog there can be an associated action that will be
performed when a line of a filename matches the pattern.
The set of patterns may appear literally as prog, or in a
file specified as -f filename.
Files are read in order; if there are no files, the standard
input is read. The filename - (a dash) means the standard
input. Each line is matched against the pattern portion of
every pattern-action statement; the associated action is
performed for each matched pattern.
An input line is made up of fields separated by white space.
(This default can be changed by using FS, vide infra.) The
fields are denoted $1, $2, ... ; $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.
An action is a sequence of statements. A statement can be
one of the following:
if ( conditional ) statement [ else statement ]
while ( conditional ) statement
for ( expression ; conditional ; expression ) statement
break
continue
{ [ statement ] ... }
variable = expression
print [ expression-list ] [ >expression ]
printf format [ , expression-list ] [ >expression ]
next # skip remaining patterns on this input line
exit # skip the rest of the input
Statements are terminated by semicolons, newlines, or right
braces. An empty expression-list stands for the whole line.
Expressions take on string or numeric values as appropriate,
and are built using the operators +, -, *, /, %, and
concatenation (indicated by a blank). The C operators ++,
Printed 4/6/89 1
AWK(1) COMMAND REFERENCE AWK(1)
--, +=, -=, *=, /=, and %= are also available in
expressions. Variables may be scalars, array elements
(denoted x[i]) or fields. Variables are initialized to the
null string. Array subscripts may be any string, not
necessarily numeric; this allows for a form of associative
memory. String constants are quoted "...".
The print statement prints its arguments on the standard
output (or on a file if >filename is present), separated by
the current output field separator, and terminated by the
output record separator. The printf statement formats its
expression list according to the format (see printf (3s)).
The built-in function length returns the length of its
argument taken as a string, or of the whole line if no
argument. There are also built-in functions exp, log, sqrt,
and int. The last truncates its argument to an integer.
substr( s, m, n) returns the n-character substring of s that
begins at position m. The function
sprintf(fmt, expr, expr, ...) formats the expressions
according to the printf (3s) format given by fmt (1mh) and
returns the resulting string.
Patterns are arbitrary Boolean combinations (!, ||, &&, and
parentheses) of regular expressions and relational
expressions. Regular expressions must be surrounded by
slashes and are as in egrep(1) . 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
an occurrence of the first pattern and the next occurrence
of the second.
A relational expression is one of the following:
expression matchop regular-expression
expression relop expression
where a relop is any of the six relational operators in C,
and a matchop is either a tilde (~) (for contains) or !~
(for does not contain). 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 must be the first pattern, END the last.
A single character c may be used to separate the fields by
starting the program with:
Printed 4/6/89 2
AWK(1) COMMAND REFERENCE AWK(1)
BEGIN { FS = "c" }
or by using the -Fc option.
Other variable names with special meanings include NF, the
number of fields in the current record; NR, the ordinal
number of the current record; FILENAME, the name of the
current input file; OFS, the output field separator (default
blank); ORS, the output record separator (default newline);
and OFMT, the output format for numbers (default "%.6g").
OPTIONS
-Fc
Designates the single character c as the field separator.
The character may be a separate argument, as in -F :
(where the field separator character is a colon). The
character t specifies that the field separator is a tab.
-ffilename
The set of patterns are contained in filename. The
filename may be a separate argument.
EXAMPLES
Print lines longer than 72 characters:
length > 72
Print first two fields in opposite order:
{ 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 }
CAVEATS
There are no explicit conversions between numbers and
strings. To force an expression to be treated as a number,
Printed 4/6/89 3
AWK(1) COMMAND REFERENCE AWK(1)
add 0 to it; to force it to be treated as a string,
concatenate quotation marks ("") to it.
When the functions log(), exp(), and sqrt() are executed
with values that are not in the domain of these functions,
or would return values that are out of the machine's range,
error messages are printed and the program terminates.
SEE ALSO
comm(1), cut(1), egrep(1), fgrep(1), grep(1), join(1),
lex(1), look(1), paste(1), regcmp(1), sed(1), sort(1),
uniq(1), exp(3m), and printf(3s).
Printed 4/6/89 4
%%index%%
na:216,98;
sy:314,216;
de:530,2239;3057,3196;6541,511;
op:7052,588;
ex:7640,644;
ca:8284,202;8774,375;
se:9149,438;
%%index%%000000000149