Test if executable exists in unix

Question

Problem

I may or may not have the executable thing in my $PATH.

How can I neatly check this in a ZSH script?

Existing Attempt

I just run the command, sending the output and errors or noman's land, then check the result code.

thing > /dev/null 2>&1
thing_installed=$?
if [ $thing_installed -eq 0 ]; then
    echo 'Thing Installed!'
fi

I feel like this could be done more neatly (one liner?).

from the man page on test ... -x file True if file exists and is executable. True indicates only that the execute flag is on. If file is a directory, true indicates that file can be searched. — devanand
– devanand, Commented Feb 15, 2014 at 19:17
Amusing that you accepted an answer that has a score of -4! — devnull
– devnull, Commented Feb 15, 2014 at 19:18
@devnull I accepted the answer which worked for me. It didn't have a -4 when I accepted it... Glad you got some amusement out of it though ;) — Pete Hamilton
– Pete Hamilton, Commented Feb 17, 2014 at 11:54
@PeterHamilton It's not a matter of being amused or not. It's sad to see unhelpful or wrong answers being accepted as those do not help any future visitors. — devnull
– devnull, Commented Feb 17, 2014 at 11:56
Which is why I changed it. Why do I feel like you're accusing me of something? :( — Pete Hamilton
– Pete Hamilton, Commented Feb 17, 2014 at 13:10

William Pursell · Accepted Answer · 2014-02-15 15:24:13Z

5

In zsh, which behaves reasonably, so you can simply do

if which thing > /dev/null 2>&1; then
    echo installed
fi

or

which thing > dev/null 2>&1 && echo installed

Note that which is a shell builtin, and its behavior is not reasonable in all shells, so this behavior cannot be relied upon.

answered Feb 15, 2014 at 15:24

William Pursell

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6 Comments

Pete Hamilton Over a year ago

Thanks, I tried this first, but the [ -e thing ] method with longform if was nicer IMO.

chepner Over a year ago

This more accurately answers your question, which specifically asked if thing was in your path.

William Pursell Over a year ago

"nicer" is an interesting definition for a solution that completely fails to work! Try test -e ls to answer the question 'is ls installed on my machine?'

devnull Over a year ago

@WilliamPursell That is the beauty of SO. You can have accepted answers that are completely wrong.

devnull Over a year ago

(It's nice to see an accepted answer with a score of -4 and counting!)

|

Adaephon · Accepted Answer · 2014-02-15 18:59:11Z

1

For zsh whence is the tool you are looking for. With parameter -p it can be forced to look only in $PATH and ignore functions, builtins and aliases with the same name.

This will either return the path to thing or an error message:

whence -cp thing

edited Feb 15, 2014 at 18:59

answered Feb 15, 2014 at 16:48

Adaephon

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Comments

user3159253 · Accepted Answer · 2014-02-15 15:25:50Z

0

use which thing and check result code

answered Feb 15, 2014 at 15:25

user3159253

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Comments

isaky · Accepted Answer · 2014-02-15 15:32:35Z

-4

You can check whether the file exists by this expresion:

[ -e thing ] && echo 'Thing Installed!'

The -e operator checks whether the file exists or not. If you want to do other file tests take a look to this page: http://tldp.org/LDP/abs/html/fto.html.

Hope this was helpful ;-)

answered Feb 15, 2014 at 15:32

isaky

12 bronze badges

2 Comments

Pete Hamilton Over a year ago

I didn't think this would work with executables, awesome, cheers.

Adaephon Over a year ago

[ -e thing] does neither check executabilty nor does it look in $PATH. For this to find anyhing thing has to be in the current directory and even then it may be a directory instead of an executable file.

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