UNIX for Dummies Questions & Answers

 
#!/bin/sh

in_path()
{
cmd=$1   path=$2   retval=1
oldIFS=$IFS   IFS-":"

for directory in $path
do
   if [ -x $direcotry/$cmd ] ; then
   retval =0
   fi
done
IFS=$oldIFS
return $retval
}

checkForCmdInPath()
{
   var=$1
   if [ "$var" != ""] ; then
      if  [ "${var%${var#?}}" = "/" ] ; then
         if [ ! -x $var ] ; then
            return 1
         fi
      elif ! in_path $var $PATH ; then
            return 2
       fi
    fi
}
    if [ $# -ne 1 ] ; then
       echo "Usage: $0 command" >&2 ; exit 1
    fi

    checkForCmdInPath "$1"
    case $? in
       0 ) echo "$1 found in PATH"      ;;
       1 ) echo "$1 not found or not executable"    ;;
       2 ) echo "$1 not found in PATH"      ;;
    esac

exit 0

IFS-":"                     # => should be IFS=":"
if [ -x $direcotry/$cmd ]   # => if [ -x $directory/$cmd ]
retval =0                   # => should be retval=0
if [ "$var" != ""] ; then   # => if [ "$var" != "" ] ; then

#!/bin/sh
# inpath - Verifies that a specified program is either valid as is, 
# or that it can be found in the PATH directory list.

in_path()
{
	# Given a command and the PATH, try to find the command.  Returns
	# 0 if found and executable, 1 if not.  Note that this temporarily modifies 
	# the IFS (input field separator) but restores it upon completion.

	cmd=$1		path=$2		retval=1
	oldIFS=$IFS	IFS=":"

	for directory in $path
	do
		if [ -x $directory/$cmd ] ; then
		retval=0   # if we're here, we found $cmd in $directory
		fi
	done
	IFS=$oldIFS
	return $retval
}

checkForCmdInPath()
{
	var=$1
	# The variable slicing notation in the following conditional
	# needs some explanation: ${var#expr} returns everything after
	# the math for 'expr' in the variable value (if any), and 
	# ${var%espr} returns everything that doesn't match (in this
	# case, just the very first character.  You can also do this in
	# Bash with ${var:0:1}, and you could use cut too: cut -c1.

	if [ "$var" != "" ] ; then
		if [ "${var%${var#?}}" = "/" ] ; then
			if [ ! -x $var ] ; then
				return 1
			fi
		elif ! in_path $var $PATH ; then
			return 2
		fi
	fi
}
	if [ $# -ne 1 ] ; then
		echo "Usage: $0 comand" >&2 ; exit 1
	fi

	checkforCmdInPath "$1"
	case $? in
		0) echo "$1 found in PATH"	;;
		1) echo "$1 not found or not executable"	;;
		2) echo "$1 not found in PATH"	;;
	esac

	exit 0