函数调用

全局函数库

您可以将所有函数存储在称为函数库的函数文件中。您可以将所有功能加载到当前脚本或命令提示符中。加载所有功能的语法如下：

. /path/to/your/functions.sh

创建一个名为 myfunctions.sh 的功能文件：

#!/bin/bash
# set variables
declare -r TRUE=0
declare -r FALSE=1
declare -r PASSWD_FILE=/etc/passwd

##################################################################
# Purpose: Converts a string to lower case
# Arguments:
#   $1 -> String to convert to lower case
##################################################################
function to_lower()
{
    local str="$@"
    local output
    output=$(tr '[A-Z]' '[a-z]'<<<"${str}")
    echo $output
}
##################################################################
# Purpose: Display an error message and die
# Arguments:
#   $1 -> Message
#   $2 -> Exit status (optional)
##################################################################
function die()
{
    local m="$1"	# message
    local e=${2-1}	# default exit status 1
    echo "$m"
    exit $e
}
##################################################################
# Purpose: Return true if script is executed by the root user
# Arguments: none
# Return: True or False
##################################################################
function is_root()
{
   [ $(id -u) -eq 0 ] && return $TRUE || return $FALSE
}

##################################################################
# Purpose: Return true $user exits in /etc/passwd
# Arguments: $1 (username) -> Username to check in /etc/passwd
# Return: True or False
##################################################################
function is_user_exits()
{
    local u="$1"
    grep -q "^${u}" $PASSWD_FILE && return $TRUE || return $FALSE
}

函数库加载

您可以将 myfunctions.sh 加载到当前的 shell 环境中，输入：

. myfunctions.sh
. /path/to/myfunctions.sh

创建一个名为 functionsdemo.sh 的脚本：

#!/bin/bash
# Load the  myfunctions.sh
# My local path is /home/vivek/lsst2/myfunctions.sh
. /home/vivek/lsst2/myfunctions.sh

# Define local variables
# var1 is not visitable or used by myfunctions.sh
var1="The Mahabharata is the longest and, arguably, one of the greatest epic poems in any language."

# Invoke the is_root()
is_root && echo "You are logged in as root." || echo "You are not logged in as root."

# Find out if user account vivek exits or not
is_user_exits "vivek" && echo "Account found." || echo "Account not found."

# Display $var1
echo -e "*** Orignal quote: \n${var1}"

# Invoke the to_lower()
# Pass $var1 as arg to to_lower()
# Use command substitution inside echo
echo -e "*** Lowercase version: \n$(to_lower ${var1})"

source

source 命令可用于将任何函数文件加载到当前的 Shell 脚本或命令提示符中。它从给定的 FILENAME 中读取并执行命令，然后返回。$PATH 中的路径名用于查找包含 FILENAME 的目录。如果提供了任何 ARGUMENTS，则它们将在执行 FILENAME 时成为位置参数。

source filename [arguments]
source functions.sh
source /path/to/functions.sh arg1 arg2
source functions.sh WWWROOT=/apache.jail PHPROOT=/fastcgi.php_jail

创建一个名为 mylib.sh 的 shell 脚本，如下所示：

#!/bin/bash
JAIL_ROOT=/www/httpd
is_root(){
   [ $(id -u) -eq 0 ] && return $TRUE || return $FALSE
}

保存并关闭文件。现在，您可以在脚本 test.sh 中使用以下语法从 mylib.sh 调用和使用函数 is_root()：

#!/bin/bash
# Load the  mylib.sh using source comamnd
source mylib.sh

echo "JAIL_ROOT is set to $JAIL_ROOT"

# Invoke the is_root() and show message to user
is_root && echo "You are logged in as root." || echo "You are not logged in as root."

我们前面的示例可以使用 source 命令更新，如下所示：

#!/bin/bash
# load myfunctions.sh function file
source /home/vivek/lsst2/myfunctions.sh

# local variable
quote="He WHO Sees me in all things, and ALL things in me, is never far from me, and I am never far from him."

# invoke is_root()
is_root && echo "You are a superuser." || echo "You are not a superuser."

# call to_lower() with ${quote}
to_lower ${quote}

递归函数

递归函数是重复调用自身的函数。递归调用的数量没有限制。创建一个名为 fact.sh 的 shell 脚本：

#!/bin/bash
# fact.sh - Shell script to to find factorial of given command line arg
factorial(){
  local i=$1
  local f
  declare -i i
  declare -i f

  # factorial() is called until the value of $f is returned and is it is <= 2
  # This is called the recursion
  [ $i -le 2 ] && echo $i || { f=$(( i - 1)); f=$(factorial $f); f=$(( f * i )); echo $f; }
}


# display usage
[ $# -eq 0 ] && { echo "Usage: $0 number"; exit 1; }

# call factorial
factorial $1

后台函数调用

＆运算符将命令放在后台，并释放终端。您也可以在后台放置一个函数。

name(){
  echo "Do something"
  sleep 1
}

# put a function in the background
name &

# do something

在执行磁带备份时，您可以显示一系列点（进度条）。这对于用户或操作员显示进度条很有用。创建一个名为 progressdots.sh 的 shell 脚本：

#!/bin/bash
# progressdots.sh - Display progress while making backup
# Based on idea presnted by nixCraft forum user rockdalinux
# Show progress dots
progress(){
  echo -n "$0: Please wait..."
  while true
  do
    echo -n "."
    sleep 5
  done
}

dobackup(){
    # put backup commands here
    tar -zcvf /dev/st0 /home >/dev/null 2>&1
}

# Start it in the background
progress &

# Save progress() PID
# You need to use the PID to kill the function
MYSELF=$!

# Start backup
# Transfer control to dobackup()
dobackup

# Kill progress
kill $MYSELF >/dev/null 2>&1

echo -n "...done."
echo

最近更新于 0001-01-01