How To Check if String Is Neither Empty nor Space in Shell Script
To check if a string is neither empty nor contains spaces in a shell script, you can use the following two methods:
Method 1: Using -n and -z Operators
The -n operator checks whether the length of the string is greater than zero, while the -z operator checks whether the length of the string is zero. We can use these operators in combination to check if a string is neither empty nor space in shell script. Here’s an example:
string=" Hello Linux "
if [ -n "${string}" ] && [ -z "$(echo ${string} | tr -d '[:space:]')" ]
then
echo "The string is empty or contains only spaces."
else
echo "The string is neither empty nor contains only spaces."
fi
In this example, we first check whether the length of the string is greater than zero using the -n operator. Then, we remove all spaces from the string using the tr command and check whether the length of the resulting string is zero using the -z operator. If both conditions are true, we can conclude that the string is neither empty nor contains only spaces.
Method 2: Using Regular Expressions
We can also use regular expressions to check whether a string is neither empty nor space in shell script. Here’s an example:
string=" Hello Linux "
if [[ "${string}" =~ ^[[:space:]]*$ ]]
then
echo "The string is empty or contains only spaces."
else
echo "The string is neither empty nor contains only spaces."
fi
In this example, we use the =~ operator to match the string against the regular expression ^[[:space:]]*$, which matches zero or more spaces at the beginning and end of the string. If the string matches this regular expression, we can conclude that it is either empty or contains only spaces.
Conclusion
In shell scripting, it is important to check whether a string is neither empty nor contains only spaces before performing any operations on it. We discussed two methods to perform this check: using -n/-z operators and using regular expressions. By using these methods, we can ensure that our shell scripts handle strings correctly and avoid unexpected errors.
