A novice will cut out a list of PIDs like this:
ps uaxw | grep nobody | cut -f 2 # huh?
ps uaxw | grep nobody | cut -f 2 -d ' ' # oh, not tabs, but spaces. huh?
ps uaxw | grep nobody | cut -f 4 -d ' ' # 'nobody' is followed by 3 spaces
After consulting 3 friends and 6 linux mailing lists about that one random
line it prints out, they learn that the canonical ways of doing this simple
task are all just horrid:
ps uaxw | grep nobody | tr -s ' ' | cut -f 4 -d ' '
ps uaxw | grep nobody | awk '{print $2}'
ps uaxw | grep nobody | while read x y z; do echo $y; done
There are two problems:
* Input is not tab delimited. It might once have been, but currently the
most interesting input is space delimited.
* There is no SIMPLE tool for handling space delimited data ({'$awk'} is not
simple, IMHO)
There are a few ways of fixing this:
1. Adding an option (-w) similar to -f to cut words separated by whitespace
(same rules as sort, unless the whitespace is changed to something else
with -d)
ps uaxwf | grep nobody | cut -w 2
ps uaxwf | grep nobody | cut --words 2
2. Adding a switch (-w) similar to set the delimiter to multiple whitespace
ps uaxwf | grep nobody | cut -w -f 2
ps uaxwf | grep nobody | cut --whitespace -f 2
3. Adding an option (-m) to merge delimiters, similar to what tr -s does, but
without having to specify the delimiter twice on the command line
ps uaxwf | grep nobody | cut -m -d ' ' -f 2
ps uaxwf | grep nobody | cut --merge-delimiters -d ' ' -f 2
4. Adding out of band meta information about the input stream, thereby
violating everything unixy, and condemning generations of children not to
understand that the scissors they are running with are sharp:
ps uaxwf | grep nobody | cut -f 2
It could be called "Alternate Data Streams" and "Extended Attributes"
5. Embark on a campaign of education and training so that the true path to
awk and tr enlightenment will be known to all.
I'm in favour of cut -w ... can I send a patch?
&:-)
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