stdin redirection

dizowned · 04-02-2008, 06:04 AM

Hey, I was wondering would anyone know why redirecting from standard in doesnt work with all basic commands? For instance if I create a text file named input with names in it say: bob and phil. Then all i want to do is execute something like "mkdir < input" or "rm < input". Either one of these commands will return to the command prompt with no work done, no error outputted or anything. Is there something about creation and deletion commands no being able to have there input redirected? I've tried this from C-Shell and Bash (I don't think the shell makes a difference, but I figured it was worth a shot).

Any replies are much appreciated, thanks.

choogendyk · 04-02-2008, 06:29 AM

try xargs.

$ cat input | xargs rmdir

I don't have a linux handy, but I've done that on Solaris and I just tried it on OpenBSD.

ta0kira · 04-02-2008, 07:22 AM

Well, if you were to type mkdir or rm without arguments would it give you the option to type something in? If not, then there's no reason for it to work with <. Many programs default to standard input for parameters when none are provided, such as cat, but for some it doesn't make sense so they don't do it. Those programs don't even attempt to read from standard input. The redirection works, but the program doesn't implement it.
ta0kira

PS You could use mkdir `cat input`.

bigearsbilly · 04-02-2008, 07:39 AM

i agree.

rm doesn't accept stdin, there you go.

use xargs as suggested.

konsolebox · 04-04-2008, 01:45 AM

you can also do

Code:

mkdir $(<input)

and to make it work with filenames that has spaces and are separated by newlines:

Code:

IFS=$'\n'
mkdir $(<input)
IFS=$' \t\n'