bash:if...then...else
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BASH - if...then...else
If takes the form:
if CONDITION then STATEMENTS fi
NOTE: The statements are only executed if the CONDITION is true.
The fi keyword is used for marking the end of the if statement.
Example
#!/bin/bash echo -n "Enter a number: " read num if [[ $num -gt 10 ]] then echo "Number is greater than 10." fi
NOTE: The above program will only show the output if the number entered is greater than ten.
The space around the [[ ]] are required!
- -gt: stands for greater than;
Similarly:
- -lt: for less than.
- -le: for less than or equal.
- -ge: for greater than or equal.
More Control Using If Else
Combining the else construct with if allows much better control over the script’s logic.
#!/bin/bash read n if [ $n -lt 10 ]; then echo "It is a one digit number" else echo "It is a two digit number" fi
The else part needs to be placed after the action part of if and before fi.
Using Elif
The elif statement stands for 'else if' and offers a convenient means for implementing chain logic.
#!/bin/bash echo -n "Enter a number: " read num if [[ $num -gt 10 ]] then echo "Number is greater than 10." elif [[ $num -eq 10 ]] then echo "Number is equal to 10." else echo "Number is less than 10." fi
See Switch
bash/if...then...else.1611664048.txt.gz · Last modified: 2021/01/26 12:27 by peter