Not working in shell script

1. Why my shell script is not working?
2. Why is my bin bash script not working?
3. Why is bash command not working?
4. What does '>' mean in shell script?
5. Why do I need #!/ Bin bash?
6. What is $() in bash?
7. How do I run bash in terminal?
8. What is $? == 0 in shell script?
9. How do I enable a script in Linux?
10. Can you run .sh in CMD?
11. What is $1 $2 in shell script?
12. What is $_ in shell?
13. What is $$ in shell?

Why my shell script is not working?

First of all make sure you have executable permission for your script. And then, Run your script using ./portblock.sh or using sh portblock.sh . If you don't like to run the script with above mentioned way then update your PATH variable to the script directory.

Why is my bin bash script not working?

bin/bash doesn't work is because you haven't provided a valid path (typically, an absolute path) to the interpreter. If you omit the initial slash / then the shell looks for bin in the current working directory but doesn't find it.

Why is bash command not working?

Sometimes when you try to use a command and Bash displays the "Command not found" error, it might be because the program is not installed on your system. Correct this by installing a software package containing the command.

What does '>' mean in shell script?

A less-than sign (<) represents input redirection. On the other hand, a greater than sign (>) is used for the output redirection.

Why do I need #!/ Bin bash?

The #!/usr/bin/bash shebang is recommended when we want to accurately point to an interpreter's absolute path. It also has relatively high security, and we can pass additional parameters. On the downside, it has poor portability because different systems can have interpreters installed in different locations.

What is $() in bash?

$( command ) or. ` command ` Bash performs the expansion by executing command in a subshell environment and replacing the command substitution with the standard output of the command, with any trailing newlines deleted. Embedded newlines are not deleted, but they may be removed during word splitting.

How do I run bash in terminal?

This method is quite easy to run a bash script, and all of them are quite simple. We just need to type in “source” before the file/script name with an extension. In a terminal, run the following code by replacing the filename with your bash script filename. The script will simply get executed after “sourcing” the file.

What is $? == 0 in shell script?

$? is the exit status of the most recently-executed command; by convention, 0 means success and anything else indicates failure. That line is testing whether the grep command succeeded. The grep manpage states: The exit status is 0 if selected lines are found, and 1 if not found.

How do I enable a script in Linux?

Create a file with .

Write the script in the file using an editor. Make the script executable with command chmod +x <fileName>. Run the script using ./<fileName>.

Can you run .sh in CMD?

The . sh file cannot be directly run on the Windows command prompt or PowerShell. Therefore, to run the . sh file on Windows, it is required to enable “Windows Subsystem for Linux” (WSL) on the system.

What is $1 $2 in shell script?

$1 - The first argument sent to the script. $2 - The second argument sent to the script. $3 - The third argument... and so forth. $# - The number of arguments provided.

What is $_ in shell?

$_ (dollar underscore) is another special bash parameter and used to reference the absolute file name of the shell or bash script which is being executed as specified in the argument list. This bash parameter is also used to hold the name of mail file while checking emails.

What is $$ in shell?

The $$ variable is the PID (Process IDentifier) of the currently running shell. This can be useful for creating temporary files, such as /tmp/my-script. $$ which is useful if many instances of the script could be run at the same time, and they all need their own temporary files.