1.test和[]命令
#!/bin/shecho
if test -z "$1"then echo "No command-line arguments."else echo "First command-line arguments is $1."fi
echo
if /usr/bin/test -z "$1"then echo "No command-line arguments."else echo "First command-line argument is $1."fi
echoif [ -z "$1" ]then echo "No command-line arguments."else echo "First command-line arguments is $1."fi
if /usr/bin/[ -z "$1" ]then echo "No command-line arguments."else echo "First command-line argument is $1."fi
echoexit 0
2.(())号命令
#! /bin/sh(( 0 ))echo "Exit status of /"(( 0 ))/" is $?."
(( 1 ))echo "Exit status of /"(( 1 ))/" is $?."
(( 5 > 4 ))echo "Exit status of /"(( 5 > 4 ))/" is $?."
(( 5 > 9 ))echo "Exit status of /"(( 5 > 9 ))/" is $?."
(( 5-5 ))echo "Exit status of /"(( 5 - 5))/" is $?."
(( 5/4 ))echo "Exit status of /"((5/4))/" is $?."
(( 1/2 ))echo "Exit status of /"((1 /2 ))/" is $?."
(( 1/0 )) 2>/dev/nullecho "Exit status of /"(( 1/0 ))/" is $?."exit 0
3.测试断掉的连接文件
#! /bin/sh[ $# -eq 0 ] && directorys=`pwd` || directorys=$@echo $@linkchk () {for element in $1/*do[ -h "$element" -a ! -e "$element" ] && echo /"$element/"[ -d "$element" ] && linkchk $elementdone}
for directory in $directorysdoif [ -d $directory ]then linkchk $directoryelse echo "$directory is not a directory" ehco "Usage: $0 dir1 dir2 ..."fi
done
exit 0
4.算术和字符串比较
#! /bin/sha=4b=5
echoif [ "$a" -ne "$b" ]then echo "$a is not equal to $b" echo "(arithmetic comparison)"fi
echo
if [ "$a" != "$b" ]then echo "$a is not equal to $b." echo "(string comparison)"fi
echoexit 0
5.检查字符串是否为null
#! /bin/shif [ -n $string1 ]then echo "String /"string/" is not null."else echo "String /"string/" is null."fi
if [ -n "$string1" ]then echo "String /"string/" is not null."else echo "String /"string/" is null."fi
if [ $string1 ]then echo "String /"string/" is not null."else echo "String /"string/" is null."fi
echo
string1=initialized
if [ $string1 ]then echo "String /"string/" is not null."else echo "String /"string/" is null."fi
string1="a = b"if [ $string1 ]then echo "String /"string/" is not null."else echo "String /"string/" is null."fi
echoexit 0
