To process the output of a command line by line (explanation):
jobs |
while IFS= read -r line; do
process "$line"
done
If you have the data in a variable already:
printf %s "$foo" | …
printf %s "$foo" is almost identical to echo "$foo", but prints $foo literally, whereas echo "$foo" might interpret $foo as an option to the echo command if it begins with a -, and might expand backslash sequences in $foo in some shells.
Note that in some shells (ash, bash, pdksh, but not ksh or zsh), the right-hand side of a pipeline runs in a separate process, so any variable you set in the loop is lost. For example, the following line-counting script prints 0 in these shells:
n=0
printf %s "$foo" |
while IFS= read -r line; do
n=$(($n + 1))
done
echo $n
A workaround is to put the remainder of the script (or at least the part that needs the value of $n from the loop) in a command list:
n=0
printf %s "$foo" | {
while IFS= read -r line; do
n=$(($n + 1))
done
echo $n
}
If acting on the non-empty lines is good enough and the input is not huge, you can use word splitting:
IFS='
'
set -f
for line in $(jobs); do
# process line
done
set +f
unset IFS
Explanation: setting IFS to a single newline makes word splitting occur at newlines only (as opposed to any whitespace character under the default setting). set -f turns off globbing (i.e. wildcard expansion), which would otherwise happen to the result of a command substitution $(jobs) or a variable substitutinosubstitution $foo. The for loop acts on all the pieces of $(jobs), which are all the non-empty lines in the command output. Finally, restore the globbing and IFS settings to values that are equivalent to the defaults.
