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This is the expected way for the awk field separator to work:

$ echo 'fooXbar' | awk 'BEGIN {FS="X"} {print $1}'
foo
$ echo 'fooXbar' | awk 'BEGIN {FS="X"} {print $2}'
bar
$ 

but if the FS is "-|-" then things get strange:

$ echo 'foo-|-bar' | awk 'BEGIN {FS="-|-"} {print $1}'
foo
$ echo 'foo-|-bar' | awk 'BEGIN {FS="-|-"} {print $2}'
|
$ echo 'foo-|-bar' | awk 'BEGIN {FS="-|-"} {print $3}'
bar
$ 

Why? Why is the $2 a "|" in the second example??

UPDATE:

$ echo 'foo-|-bar' | awk 'BEGIN {FS="-\|-"} {print $2}'
awk: warning: escape sequence `\|' treated as plain `|'
|
$ 
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2  
Multi-character field separators are treated as regular expressions in awk. You should always escape them appropriately if you want the literal meaning. –  Chris Down Feb 23 at 13:29

1 Answer 1

up vote 6 down vote accepted

FS is a regex: awk interprets -|- as "- or -".

Use -\|- instead. You'll need to double the backslash inside the string literal.

echo 'foo-|-bar' | awk 'BEGIN {FS="-\\|-"} {print $1}'

or

echo 'foo-|-bar' | awk -F '-\\|-' '{print $2}'
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