Getting number of argument passed to a shell script Post: 303003336

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Top Forums Shell Programming and Scripting Getting number of argument passed to a shell script Post 303003336 by bakunin on Tuesday 12th of September 2017 01:21:10 PM

09-12-2017

Registered User

Quote:

Originally Posted by mukulverma2408

Any idea what am I doing wrong?

Yes, and as you have already received the solution i wil concentrate on explaining the reason:

When you invoke a process with some arguments these arguments become part of the "process environment". Inside a script you can then use special variables ("$@", "$*", "$1", "$2", ...) to pull these arguments out of the environment or get ("$#") the number of parameters passed.

But every time you invoke a shell function inside a script this function gets its own environment of sorts and all the special variables "$1", "$2", etc. and "$#" describe what is passed as argument to the function instead of what is passed to the main script. Look at the following sample script:

Code:

#! /bin/bash

subfunc()
{
    echo "inside subfunc"
    echo "Number of arguments passed: $#"
    echo "argument 1: $1"
    echo "argument 2: $2"
    echo "argument 3: $3"
}

# main part
echo "inside main"
echo "Number of arguments passed: $#"
echo "argument 1: $1"
echo "argument 2: $2"
echo "argument 3: $3"

subfunc a b c
subfunc X Y

And its output will be:

Code:

# ./sample.sh foo bar baz blah
inside main
Number of arguments passed: 4
argument 1: foo
argument 2: bar
argument 3: baz
inside subfunc
Number of arguments passed: 3
argument 1: a
argument 2: b
argument 3: c
inside subfunc
Number of arguments passed: 2
argument 1: X
argument 2: Y
argument 3:

I hope this helps.

bakunin

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script

SCRIPT(1)						    BSD General Commands Manual 						 SCRIPT(1)

NAME

     script -- make typescript of terminal session

SYNOPSIS

     script [-a] [-k] [-q] [-t time] [file [command ...]]

DESCRIPTION

     The script utility makes a typescript of everything printed on your terminal.  It is useful for students who need a hardcopy record of an
     interactive session as proof of an assignment, as the typescript file can be printed out later with lpr(1).

     If the argument file is given, script saves all dialogue in file.	If no file name is given, the typescript is saved in the file typescript.

     If the argument command ... is given, script will run the specified command with an optional argument vector instead of an interactive shell.

     Options:

     -a       Append the output to file or typescript, retaining the prior contents.

     -k       Log keys sent to program as well as output.

     -q       Run in quiet mode, omit the start and stop status messages.

     -t time  Specify time interval between flushing script output file.  A value of 0 causes script to flush for every character I/O event.  The
	      default interval is 30 seconds.

     The script ends when the forked shell (or command) exits (a control-D to exit the Bourne shell (sh(1)), and exit, logout or control-d (if
     ignoreeof is not set) for the C-shell, csh(1)).

     Certain interactive commands, such as vi(1), create garbage in the typescript file.  The script utility works best with commands that do not
     manipulate the screen.  The results are meant to emulate a hardcopy terminal, not an addressable one.

ENVIRONMENT

     The following environment variable is utilized by script:

     SHELL  If the variable SHELL exists, the shell forked by script will be that shell.  If SHELL is not set, the Bourne shell is assumed.  (Most
	    shells set this variable automatically).

SEE ALSO

     csh(1) (for the history mechanism).

HISTORY

     The script command appeared in 3.0BSD.

BUGS

     The script utility places everything in the log file, including linefeeds and backspaces.	This is not what the naive user expects.

     It is not possible to specify a command without also naming the script file because of argument parsing compatibility issues.

     When running in -k mode, echo cancelling is far from ideal.  The slave terminal mode is checked for ECHO mode to check when to avoid manual
     echo logging.  This does not work when in a raw mode where the program being run is doing manual echo.

BSD
								   June 6, 1993 							       BSD