UNIX for Dummies Questions & Answers

Hi all,

I have a command I need to run on a large number of folders. It needs only one input, namely one of the 150 files in the folder (doesn't matter which one):

Code:

command filename

The problem is that the names of the files are random, so I was trying to just get the first file by using list and inputting this by making a shell variable of it, but I've had no success as a 4-month Unix newbie...

Thanks for any tips!

Well,

Code:

ls -1 | head -1

would show you the first file in the current directory.
(by the way, that is -1 as in the number 1 and not the letter L)

That sounds good, but how do I now input the output of this to a new command? I can only input the name of the file to the command (it is a custom-made medical imaging command)...

You can do it directly with one of the following two commands. depending on your unix flavor, one or both may work.

Code:

ls -l `ls -1 | head -1`
ls -l $(ls -1 | head -1)

Take a look here for examples on assigning output to variables.
https://www.unix.com/shell-programmin...-variable.html

Thanks for the reply again. I still cannot get it to work (I'm using tcsh by the way). Why do you add another ls -1?

I tried this:

Code:

set foo = $(ls -1 | head -1)
echo $foo

and

Code:

set foo = 'ls -1 | head -1'
echo $foo

But it only returns the command, not the filename.

Code:

ls -l `ls -1 | head -1`

That is LS -L in lower case
Simply a command to execute on the result of the stuff inside ` quotes.
Make sure to use the ` at the top left of the keyboard, and not the ' next to the ENTER key.