IFS bug?

[LuniTux]

Hello,

I have a script that seems to have a glitch with IFS.

If I run the script as a normal user, I get:

-rw-r--r-- root root /var/www/Shared/contacts.html
-rw-r--r-- root root /var/www/Shared/index.html
-rw-r--r-- root root /var/www/Shared/layout.css
-rw-r--r-- root root /var/www/Shared/settings.js

But if I run the script using sudo, I get:

-rw-r--r-- root root /var/www/Shared/co
tacts.html
-rw-r--r-- root root /var/www/Shared/i
dex.html
-rw-r--r-- root root /var/www/Shared/layout.css
-rw-r--r-- root root /var/www/Shared/setti
gs.js

And here is the script:

oIFS="$IFS"
IFS=$'\n'
for line in `cat 'old_permissions'`; do
	echo $line
done

It seems that the "n's" in the filenames are becoming linebreaks... Is this a glitch or is my code wrong?

Thanks,

[Vaphell]

add hashbang

#!/bin/bash

probably root doesn't use bash and the shell used doesn't recognize the $'...' construct, so the separators are $ and n

besides use while to iterate over files and command outputs, it eliminates the need for touching IFS altogether

while read -r line; do
  echo $line
done < file

while read -r line; do
  echo $line
done < <( command )

[LuniTux]

Yay that fixed it!

[asmoore82]

Mangling the IFS introduces a whole class of bugs into shell scripts that can and should be easily avoided...

#wrong, even with IFS hacks...
for file in `ls /some/dir`; do ...

#right, bug free, no IFS hacks needed...
for file in /some/dir/*; do ...

In your case:

#naughty IFS hacks...
oIFS="$IFS"
IFS=$'\n'
for line in `cat 'old_permissions'`; do
	echo $line
done

#not necessary ...
cat old_permissions | while read line
do
    echo "$line" #note below
done

Also note the quotation marks. At first glance in the following you may think that read is eating whitespace which is undesirable. But it's actually caused by the lack of quotes with the echo statement.

$ read line
test   123
$ echo $line
test 123
$ echo "$line"
test   123