Contents
How do you check if an output is empty?
To find out if a bash variable is empty:
- Return true if a bash variable is unset or set to the empty string: if [ -z “$var” ];
- Another option: [ -z “$var” ] && echo “Empty”
- Determine if a bash variable is empty: [[ ! -z “$var” ]] && echo “Not empty” || echo “Empty”
How check if file is empty shell script?
How do I check if a file is empty in Bash? You can use the find command and other options as follows. The -s option to the test builtin check to see if FILE exists and has a size greater than zero. It returns true and false values to indicate that file is empty or has some data.
How to check if a command outputs an empty string?
Here’s an alternative approach that writes the std-out and std-err of some command a temporary file, and then checks to see if that file is empty. A benefit of this approach is that it captures both outputs, and does not use sub-shells or pipes.
How to check if string not empty in Linux?
The script above stores the first command-line argument in a variable and then tests the argument in the next statement. This script will print the first argument because it is not empty. However, the output would be “First argument is empty” if nothing is contained in the argument. How to access Linux files from Windows?
How to test if a variable is empty?
To test for an empty variable you use the “if not defined” syntax (commands explicitly for variables do not require any percent signs), for example: set myvar1=foo if not defined myvar1 echo You won’t see this because %myvar1% is defined. if not defined myvar2 echo You will see this because %myvar2% isn’t defined.
Is there a way to check if output is always small?
Second, avoid unnecessary storing in RAM and processing of potentially huge data. The answer didn’t specify that the output is always small so a possibility of large output needs to be considered as well. This will run the command and check whether the returned output (string) has a zero length.