What is echo $0 in bash?

What is echo $0 in bash?

If the output of echo $0 command is -bash it means that bash was invoked as a login shell. man bash says somewhere at line 126: A login shell is one whose first character of argument zero is a -, or one started with the –login option.

What does ne mean in bash?

not equal
Following the reference to “Bash Conditional Expressions” will lead you to the description of -ne , which is the numeric inequality operator (“ne” stands for “not equal). By contrast, != is the string inequality operator.

What is ${ 1 in shell script?

1 is located to parameter ‘s position, and “$@” is located to the word ‘s one. As a result, ${1+”$@”} means… If $1 is defined, evaluate “$@” . This expression can be used in the not only Bourne shell, but also Bourne Again Shell (Bash). It seems that this is not documented on the Bash’s manual.

What does echo $1 mean?

$1 is the first command-line argument passed to the shell script. Also, know as Positional parameters. If you run ./script.sh filename1 dir1, then: $0 is the name of the script itself (script.sh) $1 is the first argument (filename1)

What is $? Ne 0 in shell script?

$? -ne 0 means previous command returned an error since 0 is considered success.

What is the meaning of $? Ne 0?

-ne 0. checks that the thing on the left ( $? ) is “not equal” to “zero”. In UNIX, a command that exits with zero succeeded, while an exit with any other value (1, 2, 3… up to 255) is a failure.

What does $1 do in bash?

$1 is the first command-line argument passed to the shell script. Also, know as Positional parameters. $0 is the name of the script itself (script.sh) $1 is the first argument (filename1) $2 is the second argument (dir1)

What does [ -NE mean in Bash?

It doesn’t mean anything “in bash”. [ runs a command called test. -ne is an argument to the test command, not to bash, and you can find its documentation in man test. By the way, this is buggy because you aren’t using quotes. It needs to be [ “$RESULT” -ne 0 ] at the minimum — or, much better, (( RESULT != 0 )).

What is the use of the exite echoes command?

Echoes (prints) the exit value for the previous command. If it failed it will be different than zero ( 0 ). Programs exit with a status code. Every program is unique and has a different set of failure codes, but it’s universally acknowledged that 0 is the ‘success’ code.

What does [$] -nE 0 mean?

in unix, 0 is the standard return code for a successful completion if [$? -ne 0] The whole line means ‘if the previous return code was not equal to 0 ‘….

What does $# mean in a bash script?

$# is typically used in bash scripts to ensure a parameter is passed. Generally you check for a parameter in the beginning of your script. To summarize $# reports the number of parameters passed to a script.