Using a command sequence

ReaperX7 · 10-03-2013, 10:01 PM

I'm currently crafting a script to use a command to check for a file before proceeding with execution of a task. I'm not very skilled with writing a script using bash, and various other tools, as usually tools like "Find" simply outputs and then stops execution.

How can I use the bash shell to generate an output that checks for a file using for example an if/else sequence, and then executes one of two commands in sequence such as this sample script (please correct as needed)

Code:

if [ -h /usr/lib/libX11.so ]; then
    echo "Found file libX11.so"
        else
        echo "Could not find libX11.so"
fi

Thank you.

Skaperen · 10-04-2013, 01:20 AM

Quote:

Originally Posted by ReaperX7

I'm currently crafting a script to use a command to check for a file before proceeding with execution of a task. I'm not very skilled with writing a script using bash, and various other tools, as usually tools like "Find" simply outputs and then stops execution.

How can I use the bash shell to generate an output that checks for a file using for example an if/else sequence, and then executes one of two commands in sequence such as this sample script (please correct as needed)

Code:

if [ -h /usr/lib/libX11.so ]; then
    echo "Found file libX11.so"
        else
        echo "Could not find libX11.so"
fi

Thank you.

You are testing if that is a symbolic link, right?

Other than a funny indent for "else" your code looks OK. I would write it like:

Code:

if [ -h /usr/lib/libX11.so ]; then
    echo "Found file libX11.so"
else
    echo "Could not find libX11.so"
fi

Then insert the command you want to run at the appropriate point

Code:

if [ -h /usr/lib/libX11.so ]; then
    echo "Found file libX11.so"
    run_me_if_file_exists
else
    echo "Could not find libX11.so"
    run_me_if_file_not_found
fi
run_me_in_either_case

SAbhi · 10-04-2013, 03:37 AM

well to check if file exists there are multiple switches that can be used:

Code:

#to check if file exists and a regular file:
[ -f /location/file-name ] && echo -e "file found and is a regular file" || echo -e "file not found"

#to check if file exists and non empty:
[ -s /location/file-name] && echo -e "file found and not empty" || echo -e "file not found"

#to check if file exists:
[ -e /location/file-name ] && echo -e "file found" || echo -e "file not found"

these are simple tests that can be done and you can incorporate same with "if" too (just for FYI).