函数定义

要定义函数，请使用以下语法：

name() compound_command ## POSIX compliant
## see the bash man page for def. of a compound command

function name { ## ksh style works in bash
 command1
 command2
}

function name() { ## bash-only hybrid
 command1
 command2
}

function name { command1; command2; commandN;}

name() { command1; command2; commandN;}

其中，name 是函数的名称，“command1; command2;”是函数中使用的命令的列表。您需要将名称替换为实际的函数名称，例如 delete_account：

rollback(){
  ...
}

add_user(){
  ...
}

delete_user(){
  ...
}

案例：NAS 挂载

定义一个名为 mount_nas 和 umount_nas 的函数：

# function to mount NAS device
mount_nas(){
        # define variables
 	NASMNT=/nas10
 	NASSERVER="nas10.nixcraft.net.in"
 	NASUSER="vivek"
 	NASPASSWORD="myNasAccountPassword"
        [ ! -d $NASMNT ] && /bin/mkdir -p $NASMNT
        mount | grep -q $NASMNT
        [ $? -eq 0 ] || /bin/mount -t cifs //$NASSERVER/$NASUSER -o username=$NASUSER,password=$NASPASSWORD $NASMNT
}

# function to unmount NAS device
umount_nas(){
	NASMNT=/nas10
  mount | grep -q $NASMNT
  [ $? -eq 0 ] && /bin/umount $NASMNT
}

您可以在 Shell 脚本的开头键入函数：

#!/bin/bash
# define variables
NASMNT=/nas10
....
..
....
# define functions
function umount_nas(){
  /bin/mount | grep -q $NASMNT
  [ $? -eq 0 ] && /bin/umount $NASMNT
}

# another function
functiom mount_nas(){
  command1
  command2
}

....
...
### main logic ##

[ $? -eq 0 ] && { echo "Usage: $0 device"; exit 1; }
...
.....

# When you wish to access function, you use the following format:
umount_nas

函数移除

要取消设置或删除该功能，请使用 unset 命令，如下所示：

unset -f functionName
unset -f hello
declare

函数参数

Shell 函数具有自己的命令行参数。使用变量 $1，$2 .. $n 访问传递给函数的参数。语法如下：

name(){
  arg1=$1
  arg2=$2
  command on $arg1
}

要调用该函数，请使用以下语法：

name foo bar

name = function name.
foo = Argument # 1 passed to the function (positional parameter # 1).
bar = Argument # 2 passed to the function.

创建一个名为 fresh.sh 的函数：

#!/bin/bash

# write a function
fresh(){
   # t stores $1 argument passed to fresh()
   t=$1
   echo "fresh(): \$0 is $0"
   echo "fresh(): \$1 is $1"
   echo "fresh(): \$t is $t"
   echo "fresh(): total args passed to me $#"
   echo "fresh(): all args (\$@) passed to me -\"$@\""
   echo "fresh(): all args (\$*) passed to me -\"$*\""
}

# invoke the function with "Tomato" argument
echo "**** calling fresh() 1st time ****"
fresh Tomato

# invoke the function with total 3 arguments
echo "**** calling fresh() 2nd time ****"
fresh Tomato Onion Paneer

可以通过以下方式访问所有函数参数或参数 $1, $2, $3,…, $N.
$0 始终指向外壳脚本名称。
$* or $@ 保存传递给函数的所有参数或参数。
$# 保留传递给函数的位置参数的数量。

#!/bin/bash
#  funcback.sh : Use $FUNCNAME
backup(){
	local d="$1"
	[[ -z $d ]] && { echo "${FUNCNAME}(): directory name not specified"; exit 1; }
	echo "Starting backup..."
}

backup $1

创建一个 shell 脚本以确定给定名称是文件还是目录（cmdargs.sh）：

#!/bin/bash
file="$1"

# User-defined function
is_file_dir(){
        # $f is local variable
	local f="$1"
        # file attributes comparisons using test i.e. [ ... ]
	[ -f "$f" ] && { echo "$f is a regular file."; exit 0; }
	[ -d "$f" ] && { echo "$f is a directory."; exit 0; }
	[ -L "$f" ] && { echo "$f is a symbolic link."; exit 0; }
	[ -x "$f" ] && { echo "$f is an executeble file."; exit 0; }
}

# make sure filename supplied as command line arg else die
[ $# -eq 0 ] && { echo "Usage: $0 filename"; exit 1; }

# invoke the is_file_dir and pass $file as arg
is_file_dir "$file"

# Sample outputs
./cmdargs.sh /etc/resolv.conf
./cmdargs.sh /bin/date
./cmdargs.sh $HOME
./cmdargs.sh /sbin

/etc/resolv.conf is a regular file.
/bin/date is a regular file.
/home/vivek is a directory.
/sbin is a directory.

最近更新于 0001-01-01