determine if value is set

[robbieg]

Hey all,

first post here and as im sure once i ask my question.. you will all know that i am very new the shell scripting. I spend all of time in php, not shell.

I need to figure out a way to see if a shell varable has a value in it.

I have

SHELL="/bin/sh"
import EXT
import HOST
VPOP="| /home/vpopmail/bin/vdelivermail '' bounce-no-mailbox"
VHOME=`/home/vpopmail/bin/vuserinfo -d $EXT@$HOST`
FILE_SIZE=$SIZE


logfile "/var/log/qmail/maildrop.log"
set -x
log "==== BEGIN maildrop processing for $EXT@$HOST ==="
log "Home directory is $VHOME"
log "File size $SIZE"

if ( $VHOME eq ' ' )
{
log "ERROR: VHOME isn't set, falling back to vdelivermail"
log "=== EXIT === "
to "$VPOP"
}

my log files show entry's for $VHOME and $FILE_SIZE and $SIZE, but yet.. my script is saying that $VHOME is empty.

Knowing that my $VHOME has a value.. what am i doing wrong that is making it process the if statement? I have tried $VHOME = '', $VHOME =='', $VHOME eq '', $VHOME eq "".

[bykwzpz]

Hey all,

first post here and as im sure once i ask my question.. you will all know that i am very new the shell scripting. I spend all of time in php, not shell.

I need to figure out a way to see if a shell varable has a value in it.

I have

SHELL="/bin/sh"
import EXT
import HOST
VPOP="| /home/vpopmail/bin/vdelivermail '' bounce-no-mailbox"
VHOME=`/home/vpopmail/bin/vuserinfo -d $EXT@$HOST`
FILE_SIZE=$SIZE


logfile "/var/log/qmail/maildrop.log"
set -x
log "==== BEGIN maildrop processing for $EXT@$HOST ==="
log "Home directory is $VHOME"
log "File size $SIZE"

if ( $VHOME eq ' ' )
{
log "ERROR: VHOME isn't set, falling back to vdelivermail"
log "=== EXIT === "
to "$VPOP"
}

my log files show entry's for $VHOME and $FILE_SIZE and $SIZE, but yet.. my script is saying that $VHOME is empty.

Knowing that my $VHOME has a value.. what am i doing wrong that is making it process the if statement? I have tried $VHOME = '', $VHOME =='', $VHOME eq '', $VHOME eq "".

Hi,

You might try -eq instead of just eq.

Hope this helped.

[robbieg]

no. that did not fix my issue.

[HTML]if ( $VHOME -eq "" )[/HTML]

[bykwzpz]

Okay, now I see the problem. The clue was that you normally operate in PHP. The if statement that you have is fine in PHP, but shell has a different structure. Try this:

[CODE]
if [ $VMHOME = "" ]
then
<what you want to do if VMHOME not set>
fi
[\CODE]

Spaces around the braces ( [ ] ) are required. I tried this on my own system and it works reliably.

[robbieg]

i now get an Syntax_error_af ter_if/ in my log files.

my code is as follows.

if [ $VHOME == '' ]
log "ERROR: VHOME isn't set, falling back to vdelivermail"
log "=== EXIT === "
to "$VPOP"
fi

[bykwzpz]

i now get an Syntax_error_af ter_if/ in my log files.

my code is as follows.

if [ $VHOME == '' ]
log "ERROR: VHOME isn't set, falling back to vdelivermail"
log "=== EXIT === "
to "$VPOP"
fi

You don't have the 'then' in your if statement. It comes right after the if line:

if [ <expession> ]
then
<statements>
fi

May also be written as:

[CODE]
if [ <expression> ] ; then
<statements>
fi
[\CODE]

Also, you will probably get some errors from your log statements. Unless you have written 'log' as a procedure call somewhere else in your shell procedure, you will get an error on each of the lines starting with 'log' and for sure on the line starting with 'to'.

In your if test expression, you are using a PHP equals. Only a single equal sign (=) is used in shell for string comparison.

[robbieg]

this is my script.

this is my script.

#! /bin/sh
import EXT
import HOST
VPOP="| /home/vpopmail/bin/vdelivermail '' bounce-no-mailbox"
VHOME=`/home/vpopmail/bin/vuserinfo -d $EXT@$HOST`
FILE_SIZE=$SIZE


logfile "/var/log/qmail/maildrop.log"
log "==== BEGIN maildrop processing for $EXT@$HOST ==="
log "Home directory is $VHOME"
log "File size $SIZE"

if [$VHOME = '' "]; then
log "ERROR: VHOME isn't set, falling back to vdelivermail"
then
log "=== EXIT === "
then
to "$VPOP"
fi

log is defined. in my script, im using 1 = sign, and i have placed my then after the ;

the script is still telling me there is an error after if on line 14.

[bykwzpz]

this is my script.

this is my script.

#! /bin/sh
import EXT
import HOST
VPOP="| /home/vpopmail/bin/vdelivermail '' bounce-no-mailbox"
VHOME=`/home/vpopmail/bin/vuserinfo -d $EXT@$HOST`
FILE_SIZE=$SIZE


logfile "/var/log/qmail/maildrop.log"
log "==== BEGIN maildrop processing for $EXT@$HOST ==="
log "Home directory is $VHOME"
log "File size $SIZE"

if [$VHOME = '' "]; then
log "ERROR: VHOME isn't set, falling back to vdelivermail"
then
log "=== EXIT === "
then
to "$VPOP"
fi

log is defined. in my script, im using 1 = sign, and i have placed my then after the ;

the script is still telling me there is an error after if on line 14.

Look at the extra quote character just before the right brace. Also, what are the extra 'then' lines doing in the script on lines above and below the 'log "=== EXIT' line?

[robbieg]

Look at the extra quote character just before the right brace. Also, what are the extra 'then' lines doing in the script on lines above and below the 'log "=== EXIT' line?

import EXT
import HOST
VPOP="| /home/vpopmail/bin/vdelivermail '' bounce-no-mailbox"
VHOME=`/home/vpopmail/bin/vuserinfo -d $EXT@$HOST`
FILE_SIZE=$SIZE


logfile "/var/log/qmail/maildrop.log"
log "==== BEGIN maildrop processing for $EXT@$HOST ==="
log "Home directory is $VHOME"
log "File size $SIZE"

if [$VHOME = '']; then
log "ERROR: VHOME isn't set, falling back to vdelivermail"
log "=== EXIT === "
to "$VPOP"
fi

same error. _Syntax_error_a fter_if/ is it worth saying that my OS is fedora 8?

[WinblowsME]

I haven't done any shell scripting in ages, but I do recall a -z string function to check if the length of the variable is zero.

http://en.wikipedia.org/wiki/Test_(Unix)

if [ -z "$variable" ] ; then
   echo "\$variable is not set."
fi

[bykwzpz]

Fedora's sh should execute like UNIX/LINUX sh, so I don't think that is the cause. Are you sure that you have spaces between the braces? I'm going to use underscore instead of space below to illustrate where spaces are required:

#example showing underscores instead of spaces
if_[_$VMHOME_=_''_]_;_then

#example showing spaces
if [ $VMHOME = '' ] ; then

This shows how to construct the expression so that VMHOME would always have a value but will still detect if it was empty. Consider this:

if [ "X$VMHOME" = "X" ] ; then
<do your log stuff here>
fi

This permits checking for an empty VMHOME, but will keep the shell from complaining if the variable is not set. I also agree with WinblowsMe's post that a -z test option is available.

[WinblowsME]

Robbie, do what bykwzpz said and put spaces around the brackets and add double-quotes to the variable.

import EXT
import HOST
VPOP="| /home/vpopmail/bin/vdelivermail '' bounce-no-mailbox"
VHOME=`/home/vpopmail/bin/vuserinfo -d $EXT@$HOST`
FILE_SIZE=$SIZE
 
logfile "/var/log/qmail/maildrop.log"
log "==== BEGIN maildrop processing for $EXT@$HOST ==="
log "Home directory is $VHOME"
log "File size $SIZE"
 
if [ "$VHOME" = "" ] ; then
   log "ERROR: VHOME isn't set, falling back to vdelivermail"
   log "=== EXIT === "
   to "$VPOP"
fi

Or try

if [ -z "$VHOME" ] ; then
   log "ERROR: VHOME isn't set, falling back to vdelivermail"
   log "=== EXIT === "
   to "$VPOP"
fi

[robbieg]

thanks everyone for all the help so far! but it's still not working for me...

#! /bin/sh
import EXT
import HOST
VPOP="| /home/vpopmail/bin/vdelivermail '' bounce-no-mailbox"
VHOME=`/home/vpopmail/bin/vuserinfo -d $EXT@$HOST`
FILE_SIZE=$SIZE


logfile "/var/log/qmail/maildrop.log"
log "==== BEGIN maildrop processing for $EXT@$HOST ==="
log "Home directory is $VHOME"
log "File size $SIZE"

if [ -z "$VHOME"  ] ; then
	log "ERROR: VHOME isn't set, falling back to vdelivermail"
	log "=== EXIT === "
	to "$VPOP"
fi

i made sure that there are spaces in my file config, and that im using the "" around my $VHOME value. log files still say ":_Syntax_error _after_if/" on line 14 which is the first time the If statement present.

[bykwzpz]

Hi Robbie,

Try this script in a separate file. I called mine 'mytest'. When you have created this script, use chmod +x to make it executable. Then execute it using ./mytest from your command prompt.

If you get the message "Error - NO VHOME", then the structure of the if statement is sound. The syntax error is somewhere else - perhaps in some of the statements within the if statement. If you don't get the message, then there may be a problem prior to the if statement that does not affect anything until the if statement is encountered.

#!/bin/sh

VHOME=""

if [ -z "$VHOME" ] ; then

echo "Error - no VMHOME"
exit 1

fi

echo "ERROR - VHOME IF TEST FAILED"

exit 0

[robbieg]

i did as u suggested.. and it said that ERROR VHOME IF TESTED FAILED.