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Comment by chaps | Hacker News Reader

No need to explicitly set FS! Just use:

echo test,123 | awk -F, '{print $1}'

Yikes. The syntax I had was wrong anyway. Should have been

   awk 'BEGIN {FS=":"};{print $1}'

One benefit of the FS variable over -F, at least in original awk, is that by using FS the delimiter can be more than one character. I guess that's why I remember FS before I remember -F. More flexible.

-F does allow multicharacter separators (at least true for me on bash shell and gawk)

    $ echo 'Sample123string42with777numbers' | awk -F'[0-9]+' '{print $2}'
    string

you were close! the following works as well

  awk -v FS="\t"

If I am not mistaken, -v is GAWK only.

So is -F, IIRC.

-F has always been supported by real UNIX®️ AWK; that's where -v and -F come from.

BUGS The -F option is not necessary given the command line variable assignment feature; it remains only for backwards compatibility.

EXAMPLES Print and sort the login names of all users:

            BEGIN     { FS = ":" }
                 { print $1 | "sort" }

The above is from the GAWK manpage. FWIW, the first example under EXAMPLES uses FS not -F.

There is nothing wrong with using FS instead of -F.

GAWK is not a real AWK!!! When will you people learn that GNU is not UNIX®️?

FS is not used on the command line and doing so is asking for trouble. FS is a built-in variable and as such is treated specially.

Every contemporary AWK supports -v. Real AWK from UNIX®️ supported -v since at least the '80's.

True. But there are differences when -v is used, as opposed to FS. Try this, where "nawk" is Lucent awk used by BSD

     cat > 1.awk << eof

     { print $ARGC }

     eof

     echo|nawk -f 1.awk FS=":"
     
     echo|gawk -f 1.awk FS=":"     
     
     echo|nawk -f 1.awk -v FS=":"

     echo|gawk -f 1.awk -v FS=":"

That is not how FS is set; It's set with -F. And there is actually no need to use -v, passing variables at the end works consistently across all AWK's and always has:

  echo "" | awk '{print Bla;}' Bla="Hello."

What if you set FS with -F but then later in the script want to change FS to something else.

The results will be unpredictable at best; either set it with -F, or use 'BEGIN {FS = "...";}', but not both.

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