Shell test command
Shell The test command is used to check whether a condition is satisfied, it can be tested numeric, character, and file three aspects.
Numerical test
| parameter | Explanation |
|---|---|
| -eq | Equal to True |
| -ne | It is not equal to True |
| -gt | Greater than True |
| -ge | Greater than or equal True |
| -lt | Less than True |
| -le | True or less |
Examples Demo:
num1=100
num2=100
if test $[num1] -eq $[num2]
then
echo '两个数相等！'
else
echo '两个数不相等！'
fi
Output:
两个数相等！
String Test
| parameter | Explanation |
|---|---|
| = | Equal to True |
| ! = | Not equal True |
| -z string | True zero-length string |
| -n string | Length of the string is not zero True |
Examples Demo:
num1="w3big"
num2="w3big"
if test num1=num2
then
echo '两个字符串相等!'
else
echo '两个字符串不相等!'
fi
Output:
两个字符串相等!
File test
| parameter | Explanation |
|---|---|
| -e filename | True if file exists |
| -r filename | If the file exists and is readable True |
| -w filename | If the file exists and is writable True |
| -x filename | If the file exists and is executable True |
| -s filename | If the file exists and that at least one character True |
| -d filename | If the file exists and is a directory True |
| -f filename | If the file exists and is a regular file True |
| -c filename | If the file exists and is a character special file True |
| -b filename | If the file exists and is a block special file True |
Examples Demo:
cd /bin
if test -e ./bash
then
echo '文件已存在!'
else
echo '文件不存在!'
fi
Output:
文件已存在!
In addition, Shell also provides a (-a), or (-o), three non-logical operators for connecting the test conditions, the priority (!): "!" Highest, "- a" time the, "- o" minimum. E.g:
cd /bin
if test -e ./notFile -o -e ./bash
then
echo '有一个文件存在!'
else
echo '两个文件都不存在'
fi
Output:
有一个文件存在!