In shell we have the command shift, but i saw on some example its giving shift 3
Why there is a number after shift ? and what its about ? what it does ?
Example:
echo “arg1= $1 arg2=$2 arg3=$3”
shift
echo “arg1= $1 arg2=$2 arg3=$3”
shift
echo “arg1= $1 arg2=$2 arg3=$3”
shift
echo “arg1= $1 arg2=$2 arg3=$3”
shift
The output will be:
arg1= 1 arg2=2 arg3=3
arg1= 2 arg2=3 arg3=
arg1= 3 arg2= arg3=
arg1= arg2= arg3=
But when i add that, it doesn't display it correctly.
The shell may be used to read and execute commands contained in a file. For example, sh file [ args ... ] calls the shell to read commands from file. Such a file is called a command procedure or shell procedure.
Shift is a builtin command in bash which after getting executed, shifts/move the command line arguments to one position left. The first argument is lost after using shift command. This command takes only one integer as an argument.
The shift command changes the values of the batch parameters %0 through %9 by copying each parameter into the previous one—the value of %1 is copied to %0, the value of %2 is copied to %1, and so on. This is useful for writing a batch file that performs the same operation on any number of parameters.
A shell script is a text file that contains a sequence of commands for a UNIX-based operating system. It is called a shell script because it combines a sequence of commands, that would otherwise have to be typed into the keyboard one at a time, into a single script.
Take a look at the man page, which says:
shift [n]
The positional parameters from n+1 ... are renamed to $1 ....
If n is not given, it is assumed to be 1.
An Example script:
#!/bin/bash
echo "Input: $@"
shift 3
echo "After shift: $@"
Run it:
$ myscript.sh one two three four five six
Input: one two three four five six
After shift: four five six
This shows that after shifting by 3, $1=four
, $2=five
and $3=six
.
you use man bash
to find the shift
builtin command:
shift [n]
The positional parameters from n+1 ... are renamed to $1 .... Parameters represented by the numbers $# down to $#-n+1 are unset. n must be a non-negative number less than or equal to $#. If n is 0, no parameters are changed. If n is not given, it is assumed to be 1. If n is greater than $#, the positional parameters are not changed. The return status is greater than zero if n is greater than $# or less than zero; otherwise 0.
This would be answered simply by reading either the Bash manual, or typing man shift
:
shift [n]
Shift the positional parameters to the left by n. The positional parameters from n+1 ... $# are renamed to $1 ... $#-n. Parameters represented by the numbers $# to $#-n+1 are unset. n must be a non-negative number less than or equal to $#. If n is zero or greater than $#, the positional parameters are not changed. If n is not supplied, it is assumed to be 1. The return status is zero unless n is greater than $# or less than zero, non-zero otherwise.
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With