001#在PATH中查找程序

验证指定程序是否有效或者能否在PATH目录列表中找到

#!/bin/bash
# 验证指定程序是否有效或者能否在PATH目录列表中找到

inpath() {
  cmd=$1
  ourpath=$2
  result=1
  oldIFS=$IFS
  IFS=":"

  for dir in $ourpath; do
    if [ -x $dir/$cmd ]; then
      result=0
    fi 
  done

  IFS=$oldIFS
  return $result
}

checkForCmdInPath() {
  var=$1
  if [ $var != "" ]; then
    if [ ${var%${var#?}} = "/" ]; then
    # 同 ${var:0:1}，提取第一个字符
      if [ ! -x $var ]; then
        return 1
      fi
    elif ! inpath $var "$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