What is $? In shell script?
-The exit status of the last command executed.
$0 -The filename of the current script.
For shell scripts, this is the process ID under which they are executing..
What is $$ in Linux?
$$ is the process ID (PID) of the script itself. $BASHPID is the process ID of the current instance of Bash. This is not the same as the $$ variable, but it often gives the same result. https://unix.stackexchange.com/questions/291570/what-is-in-bash/291577#291577.
What is $0 in bash script?
Purpose. $0 expands to the name of the shell or shell script. This is set at shell initialization. If bash is invoked with a file of commands, $0 is set to the name of that file.
What is Dirname $0?
He’s getting the script directory by doing dirname “$0″ $0 represents the first part of the command calling the script (it’s basically the inputted command without the arguments: /some/path/./script argument1 argument2. $0=”/some/path/./script” dirname basically finds the last / in a string and truncates it there.
What is the first line of shell script?
csh” is commonly used. The first line of our script is called a shebang. It consists of a number sign and an exclamation point character (#!), followed by the full path to the interpreter such as /bin/csh. All scripts under Unix execute using the interpreter specified on a first line.
What is $@ in Unix?
Save commands in files (usually called shell scripts) for re-use. … $@ refers to all of a shell script’s command-line arguments. $1 , $2 , etc., refer to the first command-line argument, the second command-line argument, etc.
What does $$ mean in bash?
The $$ is the process id of the shell in which your script is running. For more details, see the man page for sh or bash. The man pages can be found be either using a command line “man sh”, or by searching the web for “shell manpage”
What is $0 HTML?
What is $1 in bash script?
Arguments passed to the script from the command line  : $0, $1, $2, $3 . . . $0 is the name of the script itself, $1 is the first argument, $2 the second, $3 the third, and so forth.
What is Echo $1?
$1 is the argument passed for shell script. … But if you’ll write and run your own script in current session, $1, $2, … will be parameters that you send to your script.
Is Mac a Linux?
Mac OS is based on a BSD code base, while Linux is an independent development of a unix-like system. This means that these systems are similar, but not binary compatible. Furthermore, Mac OS has lots of applications that are not open source and are build on libraries that are not open source.
What is $_ in bash?
$_ :- Is a Special variable set to last argument of previous command executed. Examples:- #!/bin/bash echo $_ # /bin/bash # Just called /bin/bash to run the script.