Bash, remove numbers after colon


 
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# 8  
Old 05-13-2013
The "other shell variant" is a good one! It didn't come to me to use the IFS when i wrote my answer, but you are right. Thanks.

Quote:
Originally Posted by MadeInGermany
A shell script is slower than sed and awk and even perl if the input file is big enough.
(BTW in my measurements bash was much slower than ksh.)
We may have misunderstood each other. What i meant was this:
Code:
while read var ; do
     var=${var%%<some-subst>}
     do_something $var
     do_smth_else $var
     ...
done < /path/to/file

# whereas, very often seen:
while read var ; do
     var=$(echo $var | sed '<some-modification>')
     do_something $var
     do_smth_else $var
     ...
done < /path/to/file

In this case - where you want to extract something from the file and then do something with it inside the script - "sed" (or "awk" or any other external program) will work considerably slower than the shell built-in, regardless of using your or my method. Your method might be even a bit faster than mine, but both methods will be way faster than any external program.

But: if you want to modify the file itself, like in:

Code:
sed '<some-mod>' /path/to/input > /path/to/output

it will be the other way round: "sed" and "awk" will be fastest, "perl" considerably slower and shell only probably the slowest ("ksh" perhaps faster than "bash", because "bash" is bloated beyond belief).

I hope this helps.

bakunin
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