Shell Command Test
April 25, 2020
The command test in the shell is used to check whether a condition is true. It can test numbers, strings and files.
Number arguments test
| Tag | Description |
|---|---|
| -eq | Integer1 and Integer2 variables are algebraically equal |
| -ne | Integer1 and Integer2 variables are not algebraically equal |
| -gt | Integer1 is greater than Integer2 |
| -ge | Integer1 is greater than or equal to Integer2 |
| -lt | Integer1 is lower than Integer2 |
| -le | Integer1 is lower than or equal to Integer2 |
For example
num1=100
num2=100
if test $[num1] -eq $[num2]
then
echo 'number 1 is equal to number 2！'
else
echo 'number 1 is not equal to number 2！'
fiOutput is
number 1 is equal to number 2！[] In the code performs basic arithmetic operations, such as:
#!/bin/bash
a=15
b=14
result=$[a+b] # Note that there can be no spaces on both sides of the equal sign
echo "result is： $result"Output is
result is： 29
String arguments test
| Tag | Description |
|---|---|
| = | String1 and String2 variables are equal |
| != | String1 and String1 variables are not equal |
| -z string | Check the length of the string is zero |
| -n string | Check the length of the string is not zero |
For example
num1="linuxcommands"
num2="linuxcommands.site"
if test $num1 = $num2
then
echo 'String1 and String2 variables are equal !'
else
echo 'String1 and String2 variables are not equal!'
fiOutput is
String1 and String2 variables are not equal!File arguments test
| Tag | Description |
|---|---|
| -e FILE | FILE exists |
| -r FILE | FILE exists and read permission is granted |
| -w FILE | FILE exists and write permission is granted |
| -x FILE | FILE exists and execute permission is granted |
| -s FILE | FILE exists and has a size greater than zero |
| -d FILE | FILE exists and is a directory |
| -f FILE | FILE exists and is a regular file |
| -c FILE | FILE exists and is character special |
| -b FILE | FILE exists and is block special |
For example
cd /bin
if test -e ./bash
then
echo 'FILE exists!'
else
echo 'FILE does not exist!'
fiOutput is
FILE does not exist!In addition, shell also provides three logical operators (-a), or (-o), and not (!) which be used to connect the test conditions, and its priority is: “!” is the highest, “-a” is the second, “-o” is the lowest.
cd /bin
if test -e ./notFile -o -e ./bash
then
echo 'At least one file exists!'
else
echo 'Two files exist'
fiOutput is
At least one file exists!