Shell 系列之 declare 与 typeset

目录结构：

命令用途

常用命令参数

使用示例

命令用途

declare 与 typeset 命令是bash的内建命令，两者是完全一样的，用来声明shell变量，设置变量的属性。

常用命令参数

1. -r 设置变量为只读

2. -i 设置变量为整数

3. -a 设置变量为数组array

4. -f 如果后面没有参数的话会列出之前脚本定义的所有函数，如果有参数的话列出以参数命名的函数

5. -x 设置变量在脚本外也可以访问到

使用示例

#!/bin/bash

func1 ()
{
  echo This is a function.
}

declare -f        # Lists the function above.

echo

declare -i var1   # var1 is an integer.
var1=2367
echo "var1 declared as $var1"
var1=var1+1       # Integer declaration eliminates the need for 'let'.
echo "var1 incremented by 1 is $var1."
# Attempt to change variable declared as integer.
echo "Attempting to change var1 to floating point value, 2367.1."
var1=2367.1       # Results in error message, with no change to variable.
echo "var1 is still $var1"

echo

declare -r var2=13.36         # 'declare' permits setting a variable property
                              #+ and simultaneously assigning it a value.
echo "var2 declared as $var2" # Attempt to change readonly variable.
var2=13.37                    # Generates error message, and exit from script.

echo "var2 is still $var2"    # This line will not execute.

exit 0                        # Script will not exit here.

参考文献：

Advanced Bash-Scripting Guide

linux bash shell之declare

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