Extreme Basherism

In the past you may have encountered this problem: looping through a list of files with a Bash “for loop” gave you headaches if filenames had spaces inside. This is our setting:
<br /> flevour@voyance:/tmp/blog_post$ touch "my filename with space"<br /> flevour@voyance:/tmp/blog_post$ touch one two three other filenames<br /> flevour@voyance:/tmp/blog_post$ ls -l<br /> total 0<br /> -rw-r--r-- 1 flevour flevour 0 2007-05-07 17:49 filenames<br /> -rw-r--r-- 1 flevour flevour 0 2007-05-07 17:48 my filename with space<br /> -rw-r--r-- 1 flevour flevour 0 2007-05-07 17:49 one<br /> -rw-r--r-- 1 flevour flevour 0 2007-05-07 17:49 other<br /> -rw-r--r-- 1 flevour flevour 0 2007-05-07 17:49 three<br /> -rw-r--r-- 1 flevour flevour 0 2007-05-07 17:49 two<br />
Now, the elite hacker that is in you wants to add a cool extension to all of these. Before getting your hands dirty with mv command, you cleverly echo the variables in the for loop so you know where you are going.
First try:
<br /> flevour@voyance:/tmp/blog_post$ for i in `ls`; do echo $i; done<br /> filenames<br /> my<br /> filename<br /> with<br /> space<br /> one<br /> other<br /> three<br /> two<br />
No luck. “Maybe”, you think, “I need to add the -1 (minus-one) switch to have each filename on a single line”, no luck anyway (feel free to try), The fact is Bash “for loop” parses input stream and stops as soon as it finds a “space”. Now if you surf a bit around you may find this solution that, although very compact and easy to remember, doesn’t satisfy your unconsciously deep need for deeper hackery hacknessity:
<br /> flevour@voyance:/tmp/blog_post$ ls | while read i; do echo $i; done<br /> filenames<br /> my filename with space<br /> one<br /> other<br /> three<br /> two<br />
This solution correctly loops all the files. But I would like to show you a different approach that is obscure and great at the same time (found at LinuxQuestions):
<br /> flevour@voyance:/tmp/blog_post$ IFS=$'\n'<br /> flevour@voyance:/tmp/blog_post$ for i in `ls`; do echo $i; done<br /> filenames<br /> my filename with space<br /> one<br /> other<br /> three<br /> two<br />
Some remarks:

• it’s generally suggested to backup the original content of IFS and restore it when you don’t need the different value anymore
• IFS=$’\n’ looks strange to me, I don’t understand the need for the dollar sign. If you try with IFS=’\n’, you’ll get weird results. Any hackers out there can get the riddle an answer (Rionda? Riff Raff?)
• after some brief researches it’s not clear if IFS modification and restore is seen as a good programming pattern
• stands for Internal Field Separator

Of course the final script (we wanted to add extensions, remember?) would be:
<br /> flevour@voyance:/tmp/blog_post$ ifs=$IFS<br /> flevour@voyance:/tmp/blog_post$ IFS=$'\n'<br /> flevour@voyance:/tmp/blog_post$ for i in `ls`; do mv $i $i.1337; done<br /> flevour@voyance:/tmp/blog_post$ IFS=$ifs<br />
Enjoy your Bash hacking time!