Why different results with longhand and shorthand versions of FS?

Question

Using awk to parse a string on the command line character by character:

echo "foo" | awk 'BEGIN { FS = "" }{ for (n=1; n<=NF; n++ ) print $n }'

works fine. We can also set the value of FS on the command line. However this:

echo "foo" | awk -F '' '{ for (n=1; n<=NF; n++ ) print $n }'

yields the following error message:

awk: field separator FS is empty

Why don't both methods return identical results?

Important: GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin14)

Did you mean to miss off the trailing `'` in the second example? — Droppy, Oct 06 '15 at 09:45
mine was on ubuntu, GNU bash, version 4.3.11(1)-release (x86_64-pc-linux-gnu) and GNU Awk 4.0.1 — amdixon, Oct 06 '15 at 09:50
Have you seen [this](http://stackoverflow.com/questions/31135251/how-to-set-the-field-separator-to-an-empty-string)? (the second, unaccepted answer). — Droppy, Oct 06 '15 at 09:56

score 0 · Answer 1 · answered Nov 22 '15 at 00:55

Update your version of awk?

$ bash --version | head -n1
GNU bash, version 4.3.42(1)-release (x86_64-pc-linux-gnu)
$ gawk --version | head -n 1
GNU Awk 4.1.1, API: 1.1 (GNU MPFR 3.1.3, GNU MP 6.0.0)
$ mawk -W version
mawk 1.3.3 Nov 1996, Copyright (C) Michael D. Brennan

compiled limits:
max NF             32767
sprintf buffer      2040
$ echo "foo" | gawk -F '' '{ for (n=1; n<=NF; n++ ) print $n }'
f
o
o
$ echo "foo" | mawk -F '' '{ for (n=1; n<=NF; n++ ) print $n }'
f
o
o
$ echo "foo" | gawk 'BEGIN { FS = "" }{ for (n=1; n<=NF; n++ ) print $n }'
f
o
o
$ echo "foo" | mawk 'BEGIN { FS = "" }{ for (n=1; n<=NF; n++ ) print $n }'
f
o
o

Why different results with longhand and shorthand versions of FS?

1 Answers1