![]() In the form above, option can be one or combination of the debugging options above. The first mechanism is by altering the first line of a shell script as below, this will enable debugging of the whole script. Modifying the First Line of a Shell Script This option enables shell tracing mode.ġ. -x (short for xtrace or execution trace) – tells the shell to display all commands and their arguments on the terminal while they are executed.This options activates syntax checking mode. -n (short for noexec or no ecxecution) – instructs the shell read all the commands, however doesn’t execute them.-v (short for verbose) – tells the shell to show all lines in a script while they are read, it activates verbose mode.Methods of Enabling Shell Script Debugging Modeīelow are the primary shell script debugging options: Simply make it executable and run it as follows: $ chmod +x script_name argumentN įor scripts that do not have #! as the first line and only contain basic system commands such as the one below: #script containing standard system commandsĮcho "tmp directory created under /home/$USER" argumentNįor example: $ /bin/bash script_name argument1. argumentNĪnother possible form is by clearly specifying the shell that will execute the script as below: $ shell script_name argument1. The conventional syntax for invoking a shell script is: $ script_name argument1. Note: The first line or #! can be left out if a script contains only of a set of standard system commands, without any internal shell directives. How To Start A ScriptĪ script is distinguished from other files by its first line, that contains a #! ( She-bang – defines the file type) and a path name (path to interpreter) which informs the system that the file is a collection of commands that will be interpreted by the specified program (interpreter).īelow are examples of the “first lines” in different types of scripts: #!/bin/sh Therefore, in this shell script debugging in Linux series, we will walk through how to enable shell script debugging, move over to explain the different shell script debugging modes and how to use them in the subsequent series. However, as we begin to write very long and advanced scripts with thousands of lines of commands, for instance scripts that modify system settings, perform critical backups over networks and many more, we will realize that only looking at the output of a script is not enough to find bugs within a script. And we usually debug such scripts by doing nothing more than looking at their output and ensuring that they work as we intended. While learning scripting or during the early stages of writing scripts, we normally start by writing small or short scripts with a few lines of commands. Instead of running a sequence of commands by typing them one by one all the time on the terminal, a system user can store all of them (commands) in a file and repeatedly invokes the file to re-execute the commands several times. ![]() A script is simply a list of commands stored in a file.
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