4 ms·

To pile on :-) you often want -w (match word) flag to grep. In awk, I couldn't find how to do this. I tried /\bfoo\b/ and /\<foo\>/ but neither worked. I do

To pile on :-) you often want -w (match word) flag to grep. In awk, I couldn't find how to do this. I tried /\bfoo\b/ and /\<foo\>/ but neither worked. I don't know why and don't care enough which brings me to my major awk irritation ... It doesn't use extended or perl REs, which makes it quite different to ruby, perl, python, java. Now, according to the man page it does; at least on OSX (man re_format) but as mentioned it didn't work for me. Details $ echo fish | awk '/\bfish\b/' gets nothing, vs $ echo fish | perl -ne '/\bfish\b/ && print' fish

emmelaich 7y ago
UGH! Found the problem; it simply doesn't work. Assuming the OSX awk is the same as the freebsd awk there is a very old open bug on this: awk(1) does not support word-boundary metacharacters https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=171725 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=171725
- jolmg 7y ago
  \< and \> work with GNU's awk: $ printf "fishstick\nfish\ngoldfish\n" | awk '/\<fish\>/' fish
- asicsp 7y ago
  GNU awk supports \< and \> for start and end of word anchors, which works for GNU grep/sed as well GNU awk also supports \y which is same as \b as well as \B for opposite (same as GNU grep/sed) Intererstingly, there's a difference between the three types of word anchors: $ # \b matches both start and end of word boundaries $ # 1st and 3rd line have space as second character $ echo 'I have 12, he has 2!' | grep -o '\b..\b' I 12 , he 2 $ # \< and \> strictly match only start and end word boundaries respectively $ echo 'I have 12, he has 2!' | grep -o '\<..\>' 12 he $ # -w ensures there are no word characters around the matching text $ # same as: grep -oP '(?<!\w)..(?!\w)' $ echo 'I have 12, he has 2!' | grep -ow '..' 12 he 2!
  - emmelaich 7y ago
    Sure, but a fair bit of the value of the tool is it's consistency across platforms. There's no point in awk if perl etc are ubiquitous and more consistent.
deleted 7y ago
[deleted]
Annatar 7y ago
\b is Perl RE, not ERE. AWK not only supports ERE's, but POSIX RE's as well.

emmelaich 7y ago

UGH! Found the problem; it simply doesn't work. Assuming the OSX awk is the same as the freebsd awk there is a very old open bug on this: awk(1) does not support word-boundary metacharacters https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=171725 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=171725

jolmg 7y ago
\< and \> work with GNU's awk: $ printf "fishstick\nfish\ngoldfish\n" | awk '/\<fish\>/' fish
asicsp 7y ago
GNU awk supports \< and \> for start and end of word anchors, which works for GNU grep/sed as well GNU awk also supports \y which is same as \b as well as \B for opposite (same as GNU grep/sed) Intererstingly, there's a difference between the three types of word anchors: $ # \b matches both start and end of word boundaries $ # 1st and 3rd line have space as second character $ echo 'I have 12, he has 2!' | grep -o '\b..\b' I 12 , he 2 $ # \< and \> strictly match only start and end word boundaries respectively $ echo 'I have 12, he has 2!' | grep -o '\<..\>' 12 he $ # -w ensures there are no word characters around the matching text $ # same as: grep -oP '(?<!\w)..(?!\w)' $ echo 'I have 12, he has 2!' | grep -ow '..' 12 he 2!
- emmelaich 7y ago
  Sure, but a fair bit of the value of the tool is it's consistency across platforms. There's no point in awk if perl etc are ubiquitous and more consistent.

deleted 7y ago

[deleted]

Annatar 7y ago

\b is Perl RE, not ERE. AWK not only supports ERE's, but POSIX RE's as well.