Using the result of a command as an argument in bash?

Question

To create a playlist for all of the music in a folder, I am using the following command in bash:

ls > list.txt

I would like to use the r

Answer 1

to strip all but the directory name

ls >/playlistdir/${PWD##/*}.txt

this is probably not what you want because then you don't know where the files are (unless you change the ls command)

to replace "/" with "_"

ls >/playlistdir/${PWD//\//_}.txt

but then the playlist would look ugly and maybe not even fit in the selection window

So this will give you both a short readable name and usable paths inside the file

ext=.mp3 #leave blank for all files
for FILE in "$PWD/*$ext"; do echo "$FILE";done >/playlistdir/${PWD##/*}.txt

Answer 2

The syntax is:

ls > `pwd`.txt

That is the '`' character up underneath the '~', not the regular single quote.

Answer 3

This is equivalent to the backtick solution:

ls > $(pwd).txt

Answer 4

I suspect the problem may be that there are spaces in one of the directory names. For example, if your working directory is "/home/user/music/artist name". Bash will be confused thinking that you are trying to redirect to /home/user/music/artist and name.txt. You can fix this with double quotes

ls > "$(pwd).txt"

Also, you may not want to redirect to $(pwd).txt. In the example above, you would be redirecting the output to the file "/home/user/music/artist name.txt"

Answer 5

The best way to do this is with "$(command substitution)" (thanks, Landon):

ls > "$(pwd).txt"

You will sometimes also see people use the older backtick notation, but this has several drawbacks in terms of nesting and escaping:

ls > "`pwd`.txt"

Note that the unprocessed substitution of pwd is an absolute path, so the above command creates a file with the same name in the same directory as the working directory, but with a .txt extension. Thomas Kammeyer pointed out that the basename command strips the leading directory, so this would create a text file in the current directory with the name of that directory:

ls > "$(basename "$(pwd)").txt"

Also thanks to erichui for bringing up the problem of spaces in the path.

Answer 6

Using the above method will create the files one level above your current directory. If you want the play lists to all go to one directory you'd need to do something like:

#!/bin/sh

MYVAR=`pwd | sed "s|/|_|g"`
ls > /playlistdir/$MYVAR-list.txt