SYNOPSIS
oawk [-Fc] [-f file | prog] [file . . .]
DESCRIPTION
Oawk scans each input file for lines that match any of a set of pat-
terns specified in prog. With each pattern in prog there can be an
associated action that will be performed when a line of a file matches
the pattern. The set of patterns may appear literally as prog, or in a
file specified as -f file.
Files are read in order; if there are no files, the standard input is
read. The file name `-' 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
for ( var in array ) 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 opera-
tors +, -, *, /, %, and concatenation (indicated by a blank). The C
operators ++, --, +=, -=, *=, /=, and %= are also available in expres-
sions. Variables may be scalars, array elements (denoted x[i]) or
fields. Variables are initialized to the null string. Array sub-
scripts may be any string, not necessarily numeric; this allows for a
form of associative memory. String constants are quoted "...".
index(s,t)
the position in s where the string t occurs, or 0 if it does
not.
length(s)
returns the length of its argument taken as a string, or of the
whole line if no argument.
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 character fs or
with the field separator FS if fs is not given.
sprintf(fmt, expr, expr, ...)
formats the expressions according to the printf(3) 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.
Patterns are arbitrary Boolean combinations (!, ||, &&, and parenthe-
ses) of regular expressions and relational expressions. Regular
expressions must be surrounded by slashes and are full regular expres-
sions as described in egrep(1). Isolated regular expressions in a pat-
tern 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 ~ (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
BEGIN { FS = "c" }
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 }
ENVIRONMENT VARIABLES
LANG, LC_ALL
See locale(7).
LC_COLLATE
Determines the collation order used for string comparison.
LC_CTYPE
Maps bytes to characters.
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 C locale) is the
decimal-point character recognized in processing awk programs.
SEE ALSO
egrep(1), nawk(1), sed(1), printf(3), locale(7)
A. V. Aho, B. W. Kernighan, P. J. Weinberger, Awk - a pattern scanning
and processing language
NOTES
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.
Heirloom Toolchest 4/30/03 OAWK(1)
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