Looping through input/output Post: 302979883

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Top Forums UNIX for Beginners Questions & Answers Looping through input/output Post 302979883 by Don Cragun on Saturday 20th of August 2016 09:46:46 PM

08-20-2016

Registered User

I apologize for guessing wrong at what combining.executable does. I made the unwarranted assumption that a file named infile1 would be your 1st input file and that a file named infile2 would be your second input file instead of infile1 being the name of your 2nd input file and infile2 being the name of your 1st input file.

With that list of files and no indication of what produced it, I'll make another wild assumption that the list is the first couple of lines of output from the command:

Code:

ls *header

and that the intent is that your input files are to be processed in increasing alphanumeric sorted order. Assuming that is correct (which based on the failure of my earlier assumptions is certainly not guaranteed), the following will combine your input files and produce an output file named outfile. It uses temporary files named 0 and 1 and renames the last used temporary file to be outfile and removes the other temporary file before it exits:

Code:

#!/bin/ksh
i=0
last=0
for file in *header
do	case "$i" in
	(0)	f1=$file
		i=1
		;;
	(1)	combining.executable "$file" "$f1" > $((out = last))
		i=2
		;;
	(2)	out=$((1 - last))
		combining.executable "$file" $last > $out
		last=$out
		;;
	esac
done
mv $out "outfile"
rm -f $((1 - out))

Although written and tested using a Korn shell, this will work with any shell that uses basic Bourne shell syntax and supports POSIX arithmetic substitutions (such as ash, bash, dash, and ksh; but not csh and its derivatives, and not a traditional Bourne shell).

Don Cragun

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LEARN ABOUT DEBIAN

shcomp

SHCOMP(1)						    User Environment Utilities							 SHCOMP(1)

NAME

       shcomp - compile a ksh93 shell script

SYNOPSIS

       shcomp [ options ] [infile] [outfile]]

ORIGIN OF THIS MAN PAGE

       This man page was written by Christophe Martin <Schplurtz@free.fr> for the Debian GNU/Linux system. It is based on "shcomp --man" output.

DESCRIPTION

       Unless  -D  is  specified,  shcomp takes a shell script, infile, and creates a binary format file, outfile, that ksh93 can read and execute
       with the same effect as the original script.

       Since aliases are processed as the script is read, alias definitions whose value requires variable expansion will not work correctly.

       If -D is specified, all double quoted strings that are preceded by $ are output. These are the messages	that  need  to	be  translated	to
       locale specific versions for internationalization.

       If  outfile is omitted, then the results will be written to standard output.  If infile is also omitted, the shell script will be read from
       standard input.

OPTIONS

       -D, --dictionary
	      Generate a list of strings that need to be placed in a message catalog for internationalization.

       -n, --noexec
	      Displays warning messages for obsolete or non-conforming constructs.

       -v, --verbose
	      Displays input from infile onto standard error as it reads it.

       --man  Displays this man page on standard error and exits.

       --help Shows a short help message and exits.

EXIT STATUS

       0      Successful completion.

       >0     An error occurred.

DEBIAN WARNING

       On a Debian GNU/Linux system, more than one package may provide ksh. the output of shcomp can only be used by ksh93.  Any other ksh will be
       unable to run the compiled script.

EXAMPLE

       ( echo '#! /bin/ksh93' ; shcomp myscript ) > myscript.bin &&
       chmod 755 myscript.bin
       ./myscript.bin

SEE ALSO

       ksh(1)

IMPLEMENTATION

       version	       shcomp (AT&T Labs Research) 2012-02-29
       author	       David Korn <dgk@research.att.com>
       copyright       Copyright (c) 1982-2012 AT&T Intellectual Property
       license	       http://www.eclipse.org/org/documents/epl-v10.html

KSH93								  Fri Jun 3 2005							 SHCOMP(1)

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