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Full Discussion: usage of echo with standard input
Top Forums Shell Programming and Scripting usage of echo with standard input Post 302251531 by bakunin on Monday 27th of October 2008 10:42:30 AM
Old 10-27-2008
Quote:
Originally Posted by jim mcnamara
What is wrong with 'var="$1"'
The problem ist that $n (for n=1,2,...) denotes the first (second, ...) positional argument. In a construct like "program < file" "file" is not an argument but the "< file" creates an input stream consisting of the content of "file". A program presented with input this way will only recognize some input to its <stdin> but will not know where this is coming from. Otherwise one would have to make (different) provisions for the call "program < file" and "program < /dev/somedevice" or "program < <userinput>". But, contrary, the difference in working with a device, a file or whatever is taken care of by the operating system itself. It will take all these different data sources and turn them into "streams". Note, btw., that you can treat a file like a "clotted datastream" and a datastream like a file. This is one of the biggest avantages of UNIX designwise IMHO.

To the problem of the threadstarter:

You can always solve problems by adding another layer of indirection. ;-))

Seriously: create a small script which does only call the program itself. This script gets a positional parameter which would be the input files name:

Code:
#!/bin/ksh

fInput="$1"

print - "The input file is $fInput"

program < "$fInput"

exit $?

If your program awaits positional parameters too you have to modify this wrapper script a bit:

Code:
#!/bin/ksh

typeset fInput="$1"
typeset chOtherParms=""

shift
chOtherParms="$*"

print - "The input file is $fInput"

program $chOtherParms < "$fInput"

exit $?


If "program" is another script it would be even easier to modify it to accept an additional parameter "inputfile" and use it instead of using a pipeline. In this case post your script and we'll see how to do it if you can't do it by yourself.

I hope this helps.

bakunin
 

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LEARN ABOUT SUNOS

shift

shift(1)							   User Commands							  shift(1)

NAME

       shift - shell built-in function to traverse either a shell's argument list or a list of field-separated words

SYNOPSIS

   sh
       shift [n]

   csh
       shift [variable]

   ksh
       * shift [n]

DESCRIPTION

   sh
       The positional parameters from $n+1 ... are renamed $1 ... . If n is not given, it is assumed to be 1.

   csh
       The  components of argv, or variable, if supplied, are shifted to the left, discarding the first component. It is an error for the variable
       not to be set or to have a null value.

   ksh
       The positional parameters from $n+1 $n+1 ... are renamed $1 ..., default n is 1. The parameter n can  be  any  arithmetic  expression  that
       evaluates to a non-negative number less than or equal to $#.

       On this man page, ksh(1) commands that are preceded by one or two * (asterisks) are treated specially in the following ways:

       1.  Variable assignment lists preceding the command remain in effect when the command completes.

       2.  I/O redirections are processed after variable assignments.

       3.  Errors cause a script that contains them to abort.

       4.  Words,  following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a vari-
	   able assignment. This means that tilde substitution is performed after the = sign and word splitting and file name generation  are  not
	   performed.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       csh(1), ksh(1), sh(1), attributes(5)

SunOS 5.10							    15 Apr 1994 							  shift(1)
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