How to check the first character of a string in Bash

In this tutorial, we are going to learn about how to check the first character of a string in Bash or UNIX shell.

Consider, we have the following string:

url="/src/imgs/car.png"

Now, we need to check if the first character of the above string is slash / or not.

Checking the first character

To check the first character of a string in the bash shell, we can use the substring expansion syntax {$string::length} .

length: The number of characters we need to extract from a string.

Here is an example:

url="/src/imgs/car.png"

if [[ ${url::1} == "/" ]]
then
  echo 1;
else
  echo 0; fi

Output:

1

In the example above, we are returing 1 if a first is slash / ; otherwise we are returning 0.

Similarly, you can also check the first two characters of a string like this:

url="/src/imgs/car.png"

if [[ ${url::2} == "/s" ]]
then
  echo 1;
else
  echo 0; fi

Output:

1