1

EDIT: I KNOW THIS IS REDUNDANT, IT IS HOMEWORK, I HAVE WRITTEN MY OWN CODE AND NEED HELP TROUBLESHOOTING>

As stated, I must write a BASH script to determine whether an executable file is in the users path.

such that if you type
./findcmd ping it returns /bin/ping

I have some code written, But it does not properly work and I hope someone can help me troubleshoot. When I type ./findcmd ping it just returns my file does not exist.(with any other file I try as well that I know exists.)

#!/bin/bash
#
# Invoke as ./findcmd command
#
# Check for argument
if [[ $# -ne 1 ]]
 then
    echo 'useage: ./findcmd command'
    exit 1
fi
#
# Check for one argument
if [[ $# -eq 1 ]]
 then
     pathlist=`echo $PATH | tr ':' ' '`
     for d in $pathlist;
          do
             if [[ ! -d $d || ! -x $d || ! -r $d ]]
               then
                   echo 'You do not have read end execute
                          permissions!'
                   exit 2
              fi
              if [[ $(find $d -name $1 -print | wc -l) -ne 0 ]]
                   then
                         echo 'The file does not exist in the PATH!'
                          exit 0

             fi
        done
fi

exit 0
#
#
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7
  • is not whereis what you are looking for ? Commented May 7, 2014 at 2:56
  • 1
    There might be other problems too, but one is in: pathlist=`echo $PATH | tr ':' ' '`. You want to create an array here: pathlist=($(echo $PATH | tr ':' ' ')) Commented May 7, 2014 at 3:01
  • When you discover a path where you don't have rx permissions, why stop with exit 2? It would be better to ignore the bad paths completely and continue the loop to find one that works (if any). Commented May 7, 2014 at 3:05
  • Basically, your tests are almost the opposite of what they should be.... you want to stop when you find a path that works, otherwise keep going until you run out. Commented May 7, 2014 at 3:08
  • What happens if you eliminate the rx test for now, the first if/fi block, completely, and invert the second test, i.e. exit when find succeeds ? Commented May 7, 2014 at 3:12

2 Answers 2

Reset to default
3

No need to use a bash array, tr'ing the ':' with ' ' will work just fine in a for loop.

#!/bin/bash
#
# Invoke as ./findcmd command
#
# Check for argument
if [[ $# -ne 1 ]]
 then
    echo 'usage: ./findcmd command'
    exit 1
fi

f=$1

# No need to check the $# again, there's at least one arg and other will be ignored..
# Otherwise you can wrap this in a loop and keep shift'ing args and checking one by one
pathlist=`echo $PATH | tr ':' '\n'`
for d in $pathlist;
    do
      #echo command is your friend
      #echo "Checking for $f in $d"
      path="$d/$f"
      if [[ -f "$path" && -x "$path" ]]; then
         # PATH is not recursive, therefore no need to use find command
         # Simply checking that the file exists and is executable should be enough
         echo "Found $f at '$path'"
         # Note the same filename may be present farther down the PATH 
         # Once the first executable is found, exit
         exit 0
      fi
done

# Getting here means file was not found
echo "$f could not be found"
exit 1

Here are the results:

rbanikaz@lightsaber:~$ ./which.sh grep
Found grep at '/usr/bin/grep'
rbanikaz@lightsaber:~$ ./which.sh foo
foo could not be found
rbanikaz@lightsaber:~$
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4 Comments

This will not work if any of the directories in $PATH has a whitespace in it.
sure, changed it to tr ':' '\n' , which also works and handles spaces in directories
fyi, directories are allowed to have \n characters as well (pretty much anything but '/' for that matter). The proper way would be to temporarily set OLDIFS="$IFS" IFS=":" ... code ... IFS="$OLDIFS"
+1, but @technosaurus is correct: use IFS=':' (and restore it later) - that way you don't even need the tr command. Also, I suggest using >&2 to redirect the error messages to stderr.
-1

The which command already does this...

Techinically this is a solution...

#!/bin/bash
which $1

I probably wouldn't submit it for as assignment though...

Update

Messing around a bit and I think the following will code will get your past your current bug:

#!/bin/bash
#
# Invoke as ./findcmd command
#
# Check for argument
if [[ $# -ne 1 ]]
 then
    echo 'useage: ./findcmd command'
    exit 1
fi
#
# Check for one argument
if [[ $# -eq 1 ]]
 then
     d=$1
     pathlist=($(echo $PATH | tr ':' ' '))
     echo $pathlist

     i=0
    while read line; do
      a4[i++]=$line
    done < <(echo "$PATH" | tr ':' '\n')

    n=${#a4[@]}
    for ((i=0; i < n; i++)); do
       if [[ ! -d $d || ! -x $d || ! -r $d ]]
       then
          echo 'You do not have read end execute
                          permissions!'
          exit 2
       fi
       if [[ $(find $d -name $1 -print | wc -l) -ne 0 ]]
       then
          echo 'The file does not exist in the PATH!'
          exit 0

       fi
    done
fi

exit 0
#
#

Pretty much, it uses a solution in this SO question to split the $PATH variable into an array and then loops through it, applying the logic you had inside your while statement.

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15 Comments

How does this answer the question?
By not reinventing the wheel. If this is homework, professor should be more creative in the assignments...
It is homework, sorry if it is redundant, but I would just like some help in troubleshooting.
@Paul That's what comments are for. And it's not a case wherein one doesn't have commenting privileges.
@NSjonas The question doesn't ask you to do the homework. It posts a code snippet that is not working. You are not obliged to post an answer.
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