Bob McGowan wrote:
Jeff D wrote:
|| will not return true for you here, ever. you need to use && or use
an if statement. Also, if you are going to be using a shell script you
have to make sure that it exits properly. I would recommend putting
the whole thing into a shell script:
if ps -eaf | grep -v grep | grep -E 'cdrecord.* -[dts]ao |cdrdao \
*write|growisofs.*speed=' >> /dev/null 2>&1 ; then
logger get executed
fi
Jeff,
I'm confused, here. You say that using '||' will never work because it
will not return true. I presume you mean the '||' used in the cron
file? But, according to the the crontab man page, anything after the
fifth time column, up to the end of the line, is run by a shell, either
/bin/sh or whatever is in the SHELL variable of the crontab file.
So, '||' is just as legal as '&&' and would do just as it does on the
command line, assuming of course there is nothing found by the grep.
I don't think the problem is the use of the OR or AND operators. Rather
it's the presences or absence of the line for the grep itself being
found in the ps output.
But I may be missing something obvious?
Both are legal, but && is really what he is looking for:
[EMAIL PROTECTED]:/tmp$ nocommand || echo "ok"
bash: nocommand: command not found
ok
[EMAIL PROTECTED]:/tmp$ date|| echo "ok"
Tue Mar 18 11:35:54 PDT 2008
[EMAIL PROTECTED]:/tmp$ date && echo "ok"
Tue Mar 18 11:35:59 PDT 2008
ok
[EMAIL PROTECTED]:/tmp$ nocommand && echo "ok"
bash: nocommand: command not found
so with || we get execute command1 OR command2, whic ever one executes
first. I don't believe that this would be the desired result in this
situation.
with && we have execute command1 if it returns true execute command2
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Techno.
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