Syntax:
Any of the following syntaxes can be followed to count the length of string.
expr length $strvar
expr “${strvar}”:’.*’
$strvar | wc -c
$strvar |awk ‘{print length}’
The above syntaxes show that length of the string can be counted by any bash command or without any command. ‘#‘ symbol can be used to count the length of the string without using any command. `expr` command can be used by two ways to count the length of a string. Without `expr`, `wc` and `awk` command can also be used to count the length of a string. The uses of the mention commands and ‘#’ symbol for counting the length of the string is shown in the next part of this tutorial.
Example-1: Using the‘#’ symbol to count the length of a string
The most commonly used and simple way to count the length of a string is to use “#” symbol. The following commands will assign a value to the variable, $string and print the total number of characters of $string.
$ echo ${#string}
Output:
The following output will appear after running the above command.
Example-2: Using `expr` to count the length of a string
Another way to count the length of a string is to use `expr` command with length keyword. The following commands will assign a value to the variable, $string, store the length value to the variable, $len and print the value of $len.
$ len=`expr length "$string"`
$ echo "The length of string is $len"
Output:
The following output will appear after running the above command.
Create a bash file named “len1.sh” and add the following script. Here, a string value will be taken from the user and the length of the string value will be counted by using `expr` command that will be printed later.
len1.sh
echo “Enter a string:”
read strval
len=`expr "$strval" : ‘.*’`
echo "The length of the input string is $len"
Run the script.
Output:
Here, “I like Programming” is taken as input and the length of the string is 18.
Example-3: Using `wc` to count the length of the string
Create a bash file named “len2.sh” and add the following script. This script will read the first command-line argument into the variable $strval and count the length of $strval by using `wc` command that will be printed later.
len2.sh
strval=$1
len=`echo $strval | wc -c`
echo "The length of the first command-line argument is $len"
Run the script with one command-line argument.
Output:
The length of “Hello World” is 12 that is printed as output.
Example-4: Using `awk` to count the length of string
Create a bash file named “len3.sh” and add the following script. Here, the username will be taken as input and check the length of $username is less than 6 or not. If the length is less than 6 then the output will “Invalid username” otherwise the output will “Valid username”.
len3.sh
echo "Enter the username"
read username
len=`echo $username |awk ‘{print length}’`
if [ $len -lt 6 ]; then
echo "Invalid username"
else
echo "Valid username"
fi
Run the script.
Output:
Here, when “fahmida” is taken as the username then it is valid and when “lily” is taken as the username then it is invalid.
Conclusion:
Different ways of counting the length of a string in bash are shown in this tutorial by using various examples. The user can apply any of the mentioned ways to find out the length of the string.
