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

Question

I'm using a command-line application which is essentially a collection of bash shell scripts. The application was written to run on BSD/OSX and also on Linux. One of the scripts relies on awk. It contains two awk commands: one written for nawk (the standard BSD awk implementation) and one written for gawk (the GNU awk implementation).

The two awk commands in question are not cross-compatible with the different environments; in particular the nawk command fails when run with gawk. The script checks the kernel name (i.e. uname -s) in order to determine the host environment, and then runs the appropriate awk command. However I prefer to work on Mac OS X with the GNU core utilities installed, so the script fails to run correctly.

In the process of thinking about how best to fix this bug it occurred to me that it would be nice to know how to programmatically distinguish between different flavors of the common command-line utilities, preferably in a relatively robust and portable way.

I noticed that nawk doesn't accept the '-V' flag to print the version information, so I figured that something like the following should work:

awk -V &>/dev/null && echo gawk || echo nawk

Another variation could be:

awk -Wversion &>/dev/null && echo gawk || echo nawk

This seems to work on my two testing environments (OS X and CentOS). Here are my questions:

• Is this the best way to go?
• Is there a way to extend this to handle other variations of awk (e.g. mawk, jawk, etc.)?
• Is it even worth worrying about other versions of awk?

I should also mention that I know very little about awk.

Answer 1

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

Answer 2

Try using the which command and use its exit code.

which nawk
if [[ $? == 0 ]]; then
    command="nawk"
else
    command="gawk"
fi

then format your script to use the variable as the command

$command '{print $1}` 

would be read as

nawk '{print $1}`

if which finds nawk. Otherwise it would use gawk

Answer 3

GNU Awk is often installed as gawk, with awk as a symlink to it on systems where GNU is the default. I would guess this is the case on BSD and OS X systems, since they already have their own awk.

if gawk '{ exit; }' < /dev/null 2> /dev/null
then
    echo "gawk available"
else
    echo "gawk not available"
fi

Answer 4

A dirty hack

if nawk 'BEGIN { nawk-only-function() ;}' 
then 
   nawk -f nfile.awk ...
else 
   gawk -f gfile.awk ...
fi

• where nawk-only-function() exist only on nawk

Answer 5

I'd probably try abusing the AC_PROG_AWK m4 macro in autoconf to choose one, ordering them appropriately. It's probably overkill though

Answer 6

i have a scripted utility :

    for __ in mawk1 mawk2 gawk nawk; do
    if [ "$ZSH_VERSION" ]; then
        $( printf '%s' "$__" ) --version
    else
        eval "$__ --version"
    fi

done | mawk 'NF *= /^(GNU |m)?[Aa]wk/' OFS= \
             FS='^[[:alpha:]]+[ ]?([[:alpha:]]+[ ]+)?|[,].+$'

---

1.3.4 20230808
1.9.9.6
5.2.2
20200816

but I suppose the completely unquoted version

$__ --version

works with many shells too, but I'll stick with the safer syntax. fish shell requires some other syntax that I'm not familiar with.