shell if语句
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if
then
else
fi
test.sh: line 14: syntax error: unexpected end of fi
if
command
then
if
then
执行失败,返回非0 (grep,没找到匹配)if [ expression_r_r_r
then
then
[ -f "/etc/shadow" ] && echo"This computer uses shadow passwors"
必须:if [ i –ne 0 ]
但支持字符串变量直接if
if [ str ] 如果字符串非0
if (i )
=================================以command作为if条件===================================
echo –n “input:”
read user
if
多条指令,这些命令之间相当于“and”(与)
grep $user /etc/passwd>/tmp/null
who -u | grep $user
then
else
fi
input : macg
macg
macg has logged
# sh test.sh
input : ddd
ddd has not logged
if
以函数作为if条件,
getyn
then
echo " your answer is yes"
else
echo "your anser is no"
fi
$ vi testsh.sh
#!/bin/sh
if
cat 111-tmp.txt | grepting1
then
echo found
else
echo "no found"
fi
#!/bin/sh
cat 111-tmp.txt | grepting1
if [ $? -eq 0 ]
then
echo $?
echo found
else
echo $?
echo "no found"
fi$ sh testsh.sh
no found
1
no found$ vi 111-tmp.txt
that is 222file
thisting1 is 111file
$ sh testsh.sh
thisting1 is 111file
found$ vi 111-tmp.txt
that is 222file
thisting1 is 111file
$ sh testsh.sh
thisting1 is 111file
0
found
========================================以条件表达式作为if条件=============================
if [ 条件表达式 ]
then
else
fi
- 文件表达式
if [ -d...
if [ -s file
if [ -r file
if [ -w file
if [ -x file
- 整数变量表达式
if [ int1 -ne int2]
if [ int1 -ge int2]
if [ int1 -gt int2]
if [ int1 -le int2]
if [ int1 -lt int2]
-
字符串变量表达式
if
if
if
if
if [ a = b ];then
echo equal
else
echo no equal
fi[macg@machome ~]$ sh test.sh
input a:
5
input b:
5
no equal
if [ $a = $b ];then
echo equal
else
echo no equal
fi[macg@machome ~]$ sh test.sh
input a:
5
input b:
5
equal
[macg@machome ~]$ vi test.sh
echo -n "input your choice:"
read var
if
then
echo $var
fi
[macg@machome ~]$ sh -x test.sh
input your choice:
y
test.sh: line 3: test: y: integerexpression_r_r_r expected