Shell Programming and Scripting

#! /bin/sh
#
# Search for one or more ordinary files or file patterns on a search
# path defined by a specified environment variable.
#
# The output on standard output is normally either the full path
# to the first instance of each file found on the search path,
# or "filename: not found" on standard error.
#
# The exit code is 0 if all files are found, and otherwise a
# nonzero value equal to the number of files not found (subject
# to the shell exit code limit of 125).
#
# Usage:
# pathfind [--all] [--?] [--help] [--version] envvar pattern(s)
#
# With the --all option, every directory in the path is
# searched, instead of stopping with the first one found.

IFS='
'
OLDPATH="$PATH"
PATH=/bin:/usr/bin
export PATH
error( )
{
echo "$@" 1>&2
usage_and_exit 1
}

usage( )
{
echo "Usage: $PROGRAM [--all] [--?] [--help] [--version] envvar pattern(s)"
}

usage_and_exit( )
{
usage
exit $1
}

version( )
{
echo "$PROGRAM version $VERSION"
}

warning( )
{
echo "$@" 1>&2
EXITCODE=`expr $EXITCODE + 1`
}

all=no
envvar=
EXITCODE=0
PROGRAM=`basename $0`
VERSION=1.0

while test $# -gt 0
do
  case $1 in
	--all | --al | --a | -all | -al | -a )
	all=yes
	;;
	--help | --hel | --he | --h | '--?' | -help | -hel | -he | -h | '-?' )
	usage_and_exit 0
	;;
	--version | --versio | --versi | --vers | --ver | --ve | --v | \
	-version | -versio | -versi | -vers | -ver | -ve | -v )
	version
	exit 0
	;;
	-*)
	error "Unrecognized option: $1"
	;;
	*)
	break
	;;
  esac
  shift
done

envvar="$1"
test $# -gt 0 && shift
test "x$envvar" = "xPATH" && envvar=OLDPATH

dirpath=`eval echo '${'"$envvar"'}' 2>/dev/null | tr : ' ' `

# sanity checks for error conditions
if test -z "$envvar"
  then
  error Environment variable missing or empty
  elif test "x$dirpath" = "x$envvar"
  then
  error "Broken sh on this platform: cannot expand $envvar"
  elif test -z "$dirpath"
  then
  error Empty directory search path
  elif test $# -eq 0
  then
  exit 0
fi

# loop over argument files or patterns and directories in the search path

for pattern in "$@"
do
  result=
  for dir in $dirpath
  do
    for file in $dir/$pattern
    do
      if test -f "$file"
      then
      result="$file"
      echo $result
      test "$all" = "no" && break 2
      fi
    done
  done
  test -z "$result" && warning "$pattern: not found"
done

# Limit exit status to 125
test $EXITCODE -gt 125 && EXITCODE=125
exit $EXITCODE

test $# -eq 0 && read pattern
for pattern in "$pattern"
do
  result=
  for dir in $dirpath
  do
    for file in $dir/$pattern

if test $# -eq 0
then
  read pattern
else
  pattern=$@
fi
for pattern in "$pattern"
do
...

test $# -eq 0 && read pattern
for pattern in "$pattern"
do
  result=
  for dir in $dirpath
  do
    for file in $dir/$pattern

for pattern in "$pattern"

for pattern in "$@"
do
  result=
  for dir in $dirpath
  do
    for file in $dir/$pattern
    do
      if test -f "$file"
      then
      result="$file"
      echo $result
      test "$all" = "no" && break 2
      fi
    done
  done
  test -z "$result" && warning "$pattern: not found"
done

#!/bin/sh
if [ $# -gt 0 ]
then	for arg in "$@"
	do	printf '%s\n' "$arg"
	done
else	while IFS= read -r line
	do	printf '%s\n' "$line"
	done
fi | while IFS= read -r file
do	printf 'operand or stdin line #%d: "%s"\n' $((++cnt)) "$file"
done