test, /usr/bin/test, [ ], 和/usr/bin/[都是等价命令
#!/bin/bash
echo
if test -z "$1"
then
echo "No command-line arguments."
else
echo "First command-line argument is $1."
fi
echo
if /usr/bin/test -z "$1" # 与内建的"test"命令结果相同.
then
echo "No command-line arguments."
else
echo "First command-line argument is $1."
fi
echo
if [ -z "$1" ] # 与上边的代码块作用相同.
# if [ -z "$1" 应该能够运行, 但是...
#+ Bash报错, 提示缺少关闭条件测试的右中括号.
then
echo "No command-line arguments."
else
echo "First command-line argument is $1."
fi
echo
if /usr/bin/[ -z "$1" ] # 再来一个, 与上边的代码块作用相同.
# if /usr/bin/[ -z "$1" # 能够工作, 但是还是给出一个错误消息.
"vartify.sh" [New] 46L, 1086C written
root@client.example.com ~/yang # chmod 755 vartify.sh
root@client.example.com ~/yang # ./vartify.sh
No command-line arguments.
No command-line arguments.
No command-line arguments.
No command-line arguments.
root@client.example.com ~/yang # ./vartify.sh yangqilong
First command-line argument is yangqilong.
First command-line argument is yangqilong.
First command-line argument is yangqilong.
First command-line argument is yangqilong.
root@client.example.com ~/yang #
#!/bin/bash
echo
if test -z "$1"
then
echo "No command-line arguments."
else
echo "First command-line argument is $1."
fi
echo
if /usr/bin/test -z "$1" # 与内建的"test"命令结果相同.
then
echo "No command-line arguments."
else
echo "First command-line argument is $1."
fi
echo
if [ -z "$1" ] # 与上边的代码块作用相同.
# if [ -z "$1" 应该能够运行, 但是...
#+ Bash报错, 提示缺少关闭条件测试的右中括号.
then
echo "No command-line arguments."
else
echo "First command-line argument is $1."
fi
echo
if /usr/bin/[ -z "$1" ] # 再来一个, 与上边的代码块作用相同.
# if /usr/bin/[ -z "$1" # 能够工作, 但是还是给出一个错误消息.
"vartify.sh" [New] 46L, 1086C written
root@client.example.com ~/yang # chmod 755 vartify.sh
root@client.example.com ~/yang # ./vartify.sh
No command-line arguments.
No command-line arguments.
No command-line arguments.
No command-line arguments.
root@client.example.com ~/yang # ./vartify.sh yangqilong
First command-line argument is yangqilong.
First command-line argument is yangqilong.
First command-line argument is yangqilong.
First command-line argument is yangqilong.
root@client.example.com ~/yang #