Delimiters in Bash

May 292009

I find bash as one of the most fluid languages. Problem is when ever I come accross people that say they know bash but do not use it because they prefere perl or php. They say they use perl or php because of easy database access and how you can split strings. Today I will explain how to split a string in bash, from a stream even, so you don’t have to load whole files. I will use /etc/passwd as an example so you can follow along.

cat /etc/passwd|while read line; do

IFS=”:”

read username pass auid agid agroup ahome ashell<<EOF

$line

EOF

echo $username

echo $pass

echo $auid

echo $agid

echo $agroup

echo $ahome

echo $ashell

echo “--------”

done

Simplified version

IFS=”:”

read first_name last_name< <(echo “Jeff:Price”)

you could use this method on a never ending stream of data

Thats all for now.

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Scott M

Hmm, not working for me. Outputs just a bunch of blank lines separated by the “--------” lines.

I added #!/bin/bash at the top just to be sure and if I echo $line, it prints the lines from /etc/hosts without the colons, so it does appear to be doing something.
Jeff Price

The example was a dirty one, It may fail if the lines have comments such as #

try this in a terminal

IFS=”:”
read a b c d<<EOF
Hello:World:Apples:Oranges
EOF
echo $a
unset IFS
garywk

I played around with your script for a while and got it to work after making a few modifications.

#!/bin/bash

IFS=”:”

while read username pass auid agid agroup ahome ashell

do

echo $username

echo $pass

echo $auid

echo $agid

echo $agroup

echo $ahome

echo $ashell

echo “--------”

sleep 1

done < /etc/passwd

exit 0
xleo

Array version:

IFS=”:”; while read line; do array=($line); echo ${array[0]}; done < /etc/passwd