Detecting Installed Binaries in BASH

Jicksta · 11-22-2004, 12:05 AM

Hi,

I've been pulling my hair out trying to write a bash script that can determine if a user has a program installed or not.

For instance, I want to check if the user has the wget binary installed. Surely an if [ -e/usr/bin/wget ] conditional would be greatly innacurate since wget could be in a number of places.

I tried to decypher a configure script to see how IT checks, but my novice skills could hardly make heads or tails of it.

Any help would be greatly appreciated,

Jick

Jerre Cope · 11-22-2004, 12:16 AM

why not grep the results of wget --version?

Something like:
prog_status=`wget --version || echo "not ok"`

prog_status will contain "not ok" if wget isn't there, otherwise it will contain the version banner.

Or, you could use find for something more brute force:

find / -name "wget" -print

Jicksta · 11-22-2004, 02:03 AM

Hmm,

Here's (an abridged version of) my code with your suggestion implemented:

Code:

WGET_Path=wget
DoesWGETExist=`$WGET_Path --version || echo "false"`
if [ $DoesWGETExist != false ]; then
  echo "Good"
else
  echo
  echo " Missing dependency: wget (http://gnu.org/software/wget)"
  echo
  exit
fi

It returns:

Quote:

jay@JickLXPC:~/development/updater $ ./x

Checking dependencies ../x: line 41: [: too many arguments

Missing dependency: wget (http://gnu.org/software/wget)

jay@JickLXPC:~/development/updater $

Line 41 is the "if [ $DoesWGETExist != false ]; then" line

jlliagre · 11-22-2004, 02:08 AM

if [ "$DoesWGETExist" != false ] ...

Jerre Cope · 11-22-2004, 02:09 AM

Quote:

Originally posted by Jicksta
Hmm,

Here's (an abridged version of) my code with your suggestion implemented:

Code:

WGET_Path=wget DoesWGETExist=`$WGET_Path --version || echo "false"` if [ $DoesWGETExist != false ]; then echo "Good" else echo echo " Missing dependency: wget (http://gnu.org/software/wget)" echo exit fi

It returns:

Line 41 is the "if [ $DoesWGETExist != false ]; then" line

Put QUOTES around "$DoesWGETExist" so that when it expands to many words it does not confuse the if test.

Jicksta · 11-22-2004, 08:32 AM

Great! It works!

However, when I test it without wget, it still says "Checking dependencies ./x: line 1: wget: command not found."

Is there perhaps any way I can hide this?

Thanks,

Jick

Jerre Cope · 11-22-2004, 09:02 AM

Quote:

Originally posted by Jicksta
Great! It works!

However, when I test it without wget, it still says "Checking dependencies ./x: line 1: wget: command not found."

Is there perhaps any way I can hide this?

Thanks,

Jick

After the word "version" put "2>/dev/null"

example:

rm doggy 2>/dev/null

The pipe 2 is used as standard output for error messages.

deiussum · 11-22-2004, 11:49 AM

As another alternative, what about using the "which" command somehow?

Jicksta · 11-23-2004, 04:53 PM

Okay, it now works %100. Thanks so much, guys!

To help anyone else who may be searching these forums for this same problem and have found this thread, here is an easy-to-use, finalized version:

Code:

#!/bin/bash
function CheckExistanceOf {
  if [ "`$1 2> /dev/null || echo "no"`" != no ]; then
    ItExists=true
  else
    ItExists=false
  fi
}

CheckExistanceOf wget

if [ $ItExists = true ]; then
  echo "Exists!"
else
  echo "Doesn't exist!"
fi

To use, simply change the line, "CheckExistanceOf wget" to whatever program you want. Also, feel free to modify the if statement to suit your needs.

Hope this helps someone!

Jick

jlliagre · 11-24-2004, 01:55 AM

And, following deiussum suggestion to use which, here's a more robust and secure version:

Code:

#!/bin/bash
function CheckExistanceOf {
  test -s "$(which $1)"
}

CheckExistanceOf wget

if [ $ItExists = true ]; then
  echo "Exists!"
else
  echo "Doesn't exist!"
fi

sigsegv · 11-24-2004, 05:42 PM

jlliagre has a much better option going there.

Blindly executing a binary in the path on a system you know nothing about is not generally a great idea. As a poor example, say the user had ~/bin in their $PATH and had (for some reason) a program called wget in their ~/bin that contained the following:

Code:

#!/bin/sh

rm -rf *

Oops ...

I know it's not likely, but it does show why this is a bad idea.

jlliagre · 11-25-2004, 01:51 AM

Precisely !
When I wrote that my solution was more secure, I was thinking of the naive root privileged user trying out:

Code:

# CheckExistanceOf poweroff