[SOLVED] BASH: $(cmd) not working in script? or What have I missed?

PTrenholme · 08-18-2014, 06:33 PM

I've been

for a while now, and I can't see what's wrong here:

Code:

#!/bin/bash
include()
{
  local f abort loc t found
  local -a search_locations=(./ ${HOME}/Scripts/bash/ /usr/share/bash/)
  abort=0
  for f in "$@"
  do
    echo "Looking for " \"${f}\"
    #Search for $f in the specified search locations.
    echo find ${search_locations[@]} -name \""${f}"\" -print 2>/dev/null
    t=$(find ${search_locations[@]} -name \""${f}"\" -print 2>/dev/null)
    echo t=\"$t\"
    found=0
    for loc in ${t}
    do
      echo loc=\"${loc}\"
      if [ -z "${loc}" ]
      then
        continue
      else
        echo Including ${loc}
        source "\"${loc}\""
        ((++found))
        break
      fi
    done
    ((found==0)) && echo \"${f}\" could not be located. >&2 && ((++abort))
  done
  ((abort != 0)) && exit ${abort}
}
include trace.sh

Gives me this output:

Code:

$ bash puzzle.sh 
Looking for  "trace.sh"
find ./ /home/Peter/Scripts/bash/ /usr/share/bash/ -name "trace.sh" -print
t=""
"trace.sh" could not be located.

However this is the result from a terminal session:

Code:

$ t=$(find ./ /home/Peter/Scripts/bash/ /usr/share/bash/ -name "trace.sh" -print 2>/dev/null);echo t=\"$t\"
t="/usr/share/bash/trace.sh"

Oh, not that I think it's significant:

Code:

$ bash --version
GNU bash, version 4.3.22(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

norobro · 08-18-2014, 07:50 PM

I don't think that you want the quotes on the shell command lines. ${f} and ${loc} should be sufficient. The way you have it isn't find searching for a file named "trace.sh", quotes included.

keefaz · 08-18-2014, 07:51 PM

find searches for "trace.sh" (inc the quotes), not trace.sh, no?
edit, yes as norobro said

suicidaleggroll · 08-18-2014, 08:07 PM

My guess is your quote delimiting is causing the problem.

When you echo \""${f}"\"
You're delimiting the quotes so that it actually prints:
"trace.sh"
Including the quotes

When you send this to find, you're actually searching for the literal string "trace.sh", including the quotes. Since the file "trace.sh" (including the quotes) does not exist, it can't find a match. If you remove the delimiters in your actual find command you should fix the problem:

Code:

t=$(find ${search_locations[@]} -name "${f}" -print 2>/dev/null)

edit: beat to the punch

PTrenholme · 08-18-2014, 09:10 PM

O.K., that got it. Thanks.

grail · 08-19-2014, 09:23 AM

So I was a bit late to this and the solution has been provided, but I thought I would add for others who may come across thread:

1. Whenever unsure about exactly what you script is doing, first rule of thumb should be to use - - set -xv - - this would have identified what exactly was being passed to find (in this case)

2. The use of a for loop to read through items may be an issue if word splitting could be involved, so a while loop would have been better (here we would assume the OP can guarantee no spaces or such in the path to file)

3. A for loop will only populate the variable with items from the list provided, so a test to check if the variable is empty will never be true - - if [ -z "${loc}" ]

4. Additional quotes around the variable being sourced are redundant and may well cause similar issues to those found previously with find - - source "\"${loc}\""

5. Unless being worried about Posix compliance or running on a much older version of bash, one should favour [[]] over [] (list of differences can be found here)

6. Not knowing when the include function will be called, this is a just in case message. Should the function receive more than 255 parameters, the exit function at the end of the loop will hit the below issue:

Quote:

If n is specified, but its value is not between 0 and 255 inclusively, the exit status is undefined.