Check for File Existence Post: 302223255

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Operating Systems AIX Check for File Existence Post 302223255 by bakunin on Friday 8th of August 2008 07:30:41 PM

08-08-2008

Registered User

use the "test" command with the "-f" option. It tests for the existence of a (regular) file. You could even refine your test with the "-r" option, which tests for a regular file which has read access:

Code:

if [ -f /path/to/file ] ; then
     print - "file /path/to/file exists and is a regular file"
else
     print "file /path/to/file does not exist or is no regular file"
fi

if [ -r /path/to/file ] ; then
     print - "file /path/to/file exists and is a readable regular file"
else
     print "file /path/to/file does not exist or is not readable or no regular file"
fi

Employing the logic you use it would be possible to set a flag:

Code:

#! /bin/ksh
typeset -i lFoundSO=0
typeset    fDir="/some/where"
typeset    fFileBuffer=""

ls $fDir/SALESORDER*.dat | while read fFileBuffer ; do
     lFoundSO=1
     do_some_processing $fFileBuffer
done

if [ $lFoundSO eq 1 ] ; then
     ls $fDir/PURCHASEORDER*.dat | while read fFileBuffer ; do
          do_some_other_processing $fFileBuffer
     done
fi

if [ $lFoundSO eq 0 ] ; then
     print -u2 "Error: no SALESORDER-file found"
     exit 1
fi

exit 0

Notice that i have not used a for-loop but a while-loop instead. The reason is that the commandline has a limited length (4096 characters per POSIX 1003). As the wildcards get expanded when processing the commandline it can well be that many matching files would make a string too long for the shell to digest. You would get a "line too long-error". Therefore the while-loop and a pipeline is more safe than the for-loop.

I hope this helps.

bakunin

bakunin

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LEARN ABOUT DEBIAN

shell-quote

SHELL-QUOTE(1p) 					User Contributed Perl Documentation					   SHELL-QUOTE(1p)

NAME

       shell-quote - quote arguments for safe use, unmodified in a shell command

SYNOPSIS

       shell-quote [switch]... arg...

DESCRIPTION

       shell-quote lets you pass arbitrary strings through the shell so that they won't be changed by the shell.  This lets you process commands
       or files with embedded white space or shell globbing characters safely.	Here are a few examples.

EXAMPLES

       ssh preserving args
	   When running a remote command with ssh, ssh doesn't preserve the separate arguments it receives.  It just joins them with spaces and
	   passes them to "$SHELL -c".	This doesn't work as intended:

	       ssh host touch 'hi there'	   # fails

	   It creates 2 files, hi and there.  Instead, do this:

	       cmd=`shell-quote touch 'hi there'`
	       ssh host "$cmd"

	   This gives you just 1 file, hi there.

       process find output
	   It's not ordinarily possible to process an arbitrary list of files output by find with a shell script.  Anything you put in $IFS to
	   split up the output could legitimately be in a file's name.	Here's how you can do it using shell-quote:

	       eval set -- `find -type f -print0 | xargs -0 shell-quote --`

       debug shell scripts
	   shell-quote is better than echo for debugging shell scripts.

	       debug() {
		   [ -z "$debug" ] || shell-quote "debug:" "$@"
	       }

	   With echo you can't tell the difference between "debug 'foo bar'" and "debug foo bar", but with shell-quote you can.

       save a command for later
	   shell-quote can be used to build up a shell command to run later.  Say you want the user to be able to give you switches for a command
	   you're going to run.  If you don't want the switches to be re-evaluated by the shell (which is usually a good idea, else there are
	   things the user can't pass through), you can do something like this:

	       user_switches=
	       while [ $# != 0 ]
	       do
		   case x$1 in
		       x--pass-through)
			   [ $# -gt 1 ] || die "need an argument for $1"
			   user_switches="$user_switches "`shell-quote -- "$2"`
			   shift;;
		       # process other switches
		   esac
		   shift
	       done
	       # later
	       eval "shell-quote some-command $user_switches my args"

OPTIONS

       --debug
	   Turn debugging on.

       --help
	   Show the usage message and die.

       --version
	   Show the version number and exit.

AVAILABILITY

       The code is licensed under the GNU GPL.	Check http://www.argon.org/~roderick/ or CPAN for updated versions.

AUTHOR

       Roderick Schertler <roderick@argon.org>

perl v5.8.4							    2005-05-03							   SHELL-QUOTE(1p)