inpath

#!/usr/bin/env
# inpath--Verifies that a specified program is either valid as is or can be found in the PATH directory list
# This is practice parsing a script aloud, so the comments are egregious.

  in_path()
  {
    # Given a command and the PATH, tries to find the command. Returns zero if found and executable, 1 if not.
    # NOTE: Temporarily modified the IFS (internal field separator) but restores on completion.

    cmd=$1	ourpath=$2	result=1		# set default to 1, aka "not exe", $1 is arg following inpath
    oldIFS=$IFS	IFS=":"					# result (set default state NOPE), oldIFS save to replace
							# IFS=":" interactive mode
    for directory in "$ourpath"				# For this directory, the one we're in. Like, now.
    do						
      if [ -x $directory/$cmd ] ; then			# If full path+cmd is executable, then...
        result=0					# Update status to YUP
      fi						# for every if, there's an = and opposite fi
    done						# second verse, goto first, s/if/do s/fi/done

    IFS=$oldIFS						# Save standard IFS (" ") to restore before changing
    return $result					# 0=run it 1=keep goin
  }

  checkForCmdInPath()					# Are you ready to play NAME. THAT. FUNCTION??
  {
    # This is where you check... uhhh... for whether $cmd... y'know, man. Whether it's in the path.
    var=$1						# var = $cmd, first argument. "inpath [THISPART]"

    if [ "$var" !="" ] ; then				# if input isn't empty
      if [ "$var:0:1}" = "/" ] ; then			# see if first char behind $cmd is "/", then...
# OR     [ "${var%${var#?}}" ] ; then			# POSIX slicing method. Nested: 
							# ${print what's left after removing${extract all but first char of $var}}
							# # = delete, ? = regex for single char
# OR     [ "$(echo $var | cut -c1 )" ] ; then		# System call, cut and print first char in $var 
      if [ ! -x $var ] ; then				# see if it will NOT! run if you remove path
        return 1					# set back to 1 (NOPE)
      fi
      elif ! in_path $var "$PATH" ; then		# Otherwise, if this command exists anywhere in PATH, add it
        return 2					# add the /path/to/ part of /path/to/cmd
      fi
    fi
  }


							# Comment out the below for library use, this is for testing only

  if [ $# -ne 1 ] ; then				# If they forget to add a command
    echo "Usage: $0 command" >&				# ... remind them.
    exit 1						# Mark it NOPED
  fi

# if [ "$BASH_SOURCE" = "$0" ]				# Check if running directly or as part of another script
#							[ ADD PROMPT TO ADD PATH IF USING INTERACTIVELY ]

  checkForCmdInPath "$1"				# That thing we made? Yeah, run that thing to test it.
  case $? in						# What's your status, $?
    0 ) echo "$1 found in PATH"			;;	# yup_cmd is in a PATH dir, no /full/path/ needed.
    1 ) echo "$1 not found or not executable"	;;	# I can't find it, or it doesn't run. Either way, *shrug*
    2 ) echo "$1 not found in PATH"		::	# It... runs now, but you need to include the path part
  esac							# Waitaminute, are you by any chance related to "case"?

  exit 0						# Phew, made it. Mark it YUPPED and call it a day.