Simplifying Loopy Code

The determined Real Programmer can write FORTRAN programs in any language.

-- Ed Post, Real Programmers Don't Use PASCAL.

I just read through a friend's shell script. He doesn't program in the shell much, but he's a superb C programmer, so his script has loops that look like this:

file[0]=foo

file[1]=bar

file[2]=mumble

suffix[0]=.c

suffix[1]=.h

suffix[2]=.txt

nfiles=${#file[@]}

nsuffixes=${#suffix[@]}

i=0while [ $i -lt $nfiles ]

do

j=0

while [ $j -lt $nsuffixes ]

do

process ${file[$i]}${suffix[$j]}

(( j = j + 1 ))

done

(( i = i + 1 ))

done

Yep. That'll work. But this will, too.

for filename in {foo,bar,mumble}.{c,h,txt}

do

process $filename

done

Bash sees filenames as strings, and most shell commands accept space-separated lists of filenames. The shell handles anything that expands to a list of filenames, like globs or brace expansions, with real ease.

Use the Shell, Luke.