Difference between gawk vs. awk

awkgawk

Trying to understand the differences between the two functions gawk vs. awk? When would one use gawk vs awk? Or are they the same in terms of usage?

Also, could one provide an example?

Best Answer

AWK is a programming language. There are several implementations of AWK (mostly in the form of interpreters). AWK has been codified in POSIX. The main implementations in use today are:

nawk (“new awk”, an evolution of oawk, the original UNIX implementation), used on *BSD and widely available on Linux;
mawk, a fast implementation that mostly sticks to standard features;
gawk, the GNU implementation, with many extensions;
the Busybox (small, intended for embedded systems, not many features).

If you only care about standard features, call awk, which may be Gawk or nawk or mawk or some other implementation. If you want the features in GNU awk, use gawk or Perl or Python.

Related Solutions

Why can’t a constant regular expression be put on the left side of an ~ operator in gawk

To quote the POSIX spec for awk:

When an ERE token appears as an expression in any context other than as the right-hand of the ~ or !~ operator or as one of the built-in function arguments described below, the value of the resulting expression shall be the equivalent of:

$0 ~ /ere/

This (combined with the action defaulting to { print }) is why you can use awk as a grep substitute by just doing awk '/b/' <file.

So, the answer is just "it's defined to work that way". /ere/ is defined to mean $0 ~ /ere/ except in certain circumstances, and /ere/ ~ $1 is not one of the exceptional circumstances, so it gets evaluated as ($0 ~ /ere/) ~ $1.

Shell – How to programmatically detect awk flavor (e.g. gawk vs nawk)

if awk --version 2>&1 | grep -q "GNU Awk"
then
    awk 'BEGIN {print "I am GNU Awk"}'

elif awk -Wv 2>&1 | grep -q "mawk"
then
    awk 'BEGIN {print "I am mawk"}'

else
    awk 'BEGIN {print "I might be nawk, might not be"}'
fi

Alternatively, test is awk is a symbolic link:

awk=$( command -v awk )
[[ -L $awk ]] && readlink $awk # make some decision about the result of that

Best Answer

Related Solutions

Why can’t a constant regular expression be put on the left side of an ~ operator in gawk

Shell – How to programmatically detect awk flavor (e.g. gawk vs nawk)

Related Question