What is the meaning of $# in shell scripts?

ravi_nandula · 03-28-2012, 02:05 AM

Hi everyone,
What is the meaning of the below line in scripting
if [ $# -ne 1 ]

xiaokun · 03-28-2012, 02:07 AM

$# means arguments' number . -ne means !=

xiaokun · 03-28-2012, 02:09 AM

FYI
$0 script name
$1 first argument
$2 second ..
$@ all argument
$* all arguments in one string
$$ current pid
$? exit status

ravi_nandula · 03-28-2012, 02:09 AM

Hey xiaokun,
Arguments???I did not get you correctly

ravi_nandula · 03-28-2012, 02:10 AM

okok.
can you suggest me one website for preparing scripting........

xiaokun · 03-28-2012, 02:18 AM

For example, in script hello.sh

#!/bin/bash
echo $#
echo "hello world"

when u run as ./hello.sh 0 1 2
it will show:
3
hello world

website.... u should google it

colucix · 03-28-2012, 02:38 AM

Quote:

Originally Posted by ravi_nandula

okok.
can you suggest me one website for preparing scripting........

I'd suggest a really good reading on the Linux command line in general (shell scripting included): http://linuxcommand.org/tlcl.php (check the on-line version). Another good resource is the Linux Documentation Project http://www.tldp.org (check the longer in-depth guides, e.g. The Bash Guide for Beginners). Hope this helps.

ravi_nandula · 03-28-2012, 03:06 AM

thank you Colucix...

ravi_nandula · 03-28-2012, 03:10 AM

hey ,

I need a script that prints name of person...by taking it as string.....say s1 n s2 and will finally print the full name i.e,. (s1 + s2).
s1 - raj
s2 - sekhar
.....I need output as " raj sekhar".....

please help mee............
----------------------------------
do we have strings in scripting?????????

colucix · 03-28-2012, 03:20 AM

Input from the user is acquired by the read statement. Simple printing out is performed by echo (properly use double quotes to put a space between the two strings).

At this point I strongly suggest to start reading the aforementioned book. You will learn a lot and if you're stuck at some point feel free to ask. Always post what have you tried and give as many details as possible on error messages (if any) or unexpected behaviour of your code, specifying the input and the desired output. Using CODE tags is also advisable to improve readability of the posted code and preserve spacing and indentation.

To use CODE tags, either put [CODE] and [/CODE] around the text or switch to Advanced Mode (see the Go Advanced button at the bottom of the Quick Reply box), select the text and press the # button. The CODE tags will be added automatically.

Finally, please don't post multiple questions in the same thread: the discussion is difficult to follow and your new questions will not have the visibility they deserve. Thank you.

devUnix · 03-28-2012, 04:19 AM

Quote:

Originally Posted by ravi_nandula

hey ,

I need a script that prints name of person...by taking it as string.....say s1 n s2 and will finally print the full name i.e,. (s1 + s2).
s1 - raj
s2 - sekhar
.....I need output as " raj sekhar".....

please help mee............
----------------------------------
do we have strings in scripting?????????

Code:

read -p "First Name: " F_NAME
read -p "Last Name: " L_NAME
echo "Welcome, $F_NAME $L_NAME"

Save it as example.sh

and then do this to set the execution bit on:

Code:

chmod 755 example.sh

and then this to run the script:

Code:

./example.sh

Add this line at the top of the script file (recommended and is the best practice):

Code:

#!/bin/bash

check the correct path on your system by executing this command:

Code:

which bash

.

devUnix · 03-28-2012, 04:25 AM

Quote:

Originally Posted by ravi_nandula

Hey xiaokun,
Arguments???I did not get you correctly

Whatever you specify after a script's/program's name is called Command-Line Argument. Examples:

Code:

ls fileName
file fileName
./myScript.sh arg1 arg2 argn

In your script you will access arg1 by saying $1 and so on up to $9. Refer to the bash guide on www.tldp.org for more details.

ravi_nandula · 03-28-2012, 04:34 AM

Quote:

Originally Posted by devUnix

Whatever you specify after a script's/program's name is called Command-Line Argument. Examples:

Code:

ls fileName
file fileName
./myScript.sh arg1 arg2 argn

In your script you will access arg1 by saying $1 and so on up to $9. Refer to the bash guide on www.tldp.org for more details.

yah.Now I got your point.

ravi_nandula · 03-28-2012, 04:35 AM

hey I need one more script
That will print the wishes like gud morning,eveng n night.....whenever system gets booted.......?

devUnix · 03-28-2012, 05:16 AM

Quote:

Originally Posted by ravi_nandula

hey I need one more script
That will print the wishes like gud morning,eveng n night.....whenever system gets booted.......?

Ravi, you need bash Beginner's Guide or Advanced Bash Scripting Guide found on www.tldp.org

To run anything at log-in, edit your .bash_profile file found your home directory (the one that you are placed in when you log-in to your Unix/Linux system). Check it by issuing this command:

Code:

ls -ld .*

or

Code:

ls -la

You should see files ending in "profile" beginning with ".". It could be .profile or .bash_profile or .sh_profile. Usually, it is your "profile" file that is executed whenever your log-in to your system. Similarly there is a .logout file whose function should be obvious now.

So, add this line at the end of your .profile file:

Code:

echo "Hello, ${USER}!"

and add these lines at the end of your .logout file:

Code:

echo "Bye, ${USER}!"
read -p "Press enter to log out..."

You can actually do more than that. Just keep your codes in a separate script file and then call it from within any of the above files:

Code:

./myScript.sh

A Note on the Variable: We enclose the variable's name with curly braces in case any other character or word is adjacent to it so that it is separately taken as a variable and not as a part of the other word. In the above case, we have separated the variable's name from the exclamation mark.

To check your home directory issue this command at the Command Prompt / Shell Prompt:

Code:

echo $HOME

To directly get into your home directory, do this:

Code:

cd

Yes, no argument is supplied this time. $HOME is taken by default.