Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
This defaults to whitespace (space, tab, and newline), but may be changed, for example, to parse a
comma−separated data file. Note that $* uses the first character held in $IFS. See Example 5−1.
bash$ echo $IFS | cat −vte
$
bash$ bash −c 'set w x y z; IFS=":−;"; echo "$*"'
w:x:y:z
$IFS does not handle whitespace the same as it does other characters.
Example 9−1. $IFS and whitespace
#!/bin/bash
# $IFS treats whitespace differently than other characters.
output_args_one_per_line()
{
for arg
do echo "[$arg]"
done
}
echo; echo "IFS=\" \""
echo "−−−−−−−"
IFS=" "
var=" a b c "
output_args_one_per_line $var # output_args_one_per_line `echo " a b c "`
#
# [a]
# [b]
# [c]
echo; echo "IFS=:"
echo "−−−−−"
IFS=:
var=":a::b:c:::" # Same as above, but substitute ":" for " ".
output_args_one_per_line $var
#
# []
# [a]
# []
# [b]
# [c]
# []
# []
# []
# The same thing happens with the "FS" field separator in awk.
# Thank you, Stephane Chazelas.
echo
exit 0
Chapter 9. Variables Revisited 66