Re: /bin/sh Madness
Dan Nelson wrote:
In the last episode (Feb 16), Tim Daneliuk said:
Here is a shell function that behaves quite strangely:
#!/bin/sh
#
# Execute A Command, Noting Start/Stop Time, Logging Output
# Args:
# $1 Command Name
# $2 Log Directory
# $3 Command String To Execute
#
runupd()
{
log=$2/$1.log
timestamp $log
touch $2/.$1-begin eval $3 21 $log touch $2/.$1-end
}
# End of 'runupd()'
So, you might do something like:
runupd freespace /var/log/ df -k
Now, for the weirdness. This function works fine in my script
so long as one of two conditions is met:
1) I run it interactively from the command line (bash)
OR
2) I run it from 'cron' AND $3 is *not* another script
If I try to run it from 'cron' and point $3 to a script, everything gets
run as planned, however, the ending timestamp (touch $2/.$1-end) never
runs. That is, the initial time stamp (.$1-begin) and the command itself
are executed, and output is properly written to the logfile,
but the final timestamp never happens.
Could your $3 command be returning a nonzero exit code? You probably
want something more like
touch $2/.$1-begin { eval $3 21 $log ; touch $2/.$1-end }
I am looking into this.
so your end timestamp always gets created whether or not $3 succeeds.
Also note that in your original script, you only backgrounded touch
$2/.$1-end, which is probably not what you wanted.
H - I have invoked the script that uses this function a variety
of ways and the command being evaled *is* being backgrounded in
every case with the syntax shown above ...
--
Tim Daneliuk [EMAIL PROTECTED]
PGP Key: http://www.tundraware.com/PGP/
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Re: /bin/sh Madness
Dan Nelson wrote:
In the last episode (Feb 16), Tim Daneliuk said:
Here is a shell function that behaves quite strangely:
#!/bin/sh
#
# Execute A Command, Noting Start/Stop Time, Logging Output
# Args:
# $1 Command Name
# $2 Log Directory
# $3 Command String To Execute
#
runupd()
{
log=$2/$1.log
timestamp $log
touch $2/.$1-begin eval $3 21 $log touch $2/.$1-end
}
# End of 'runupd()'
So, you might do something like:
runupd freespace /var/log/ df -k
Now, for the weirdness. This function works fine in my script
so long as one of two conditions is met:
1) I run it interactively from the command line (bash)
OR
2) I run it from 'cron' AND $3 is *not* another script
If I try to run it from 'cron' and point $3 to a script, everything gets
run as planned, however, the ending timestamp (touch $2/.$1-end) never
runs. That is, the initial time stamp (.$1-begin) and the command itself
are executed, and output is properly written to the logfile,
but the final timestamp never happens.
Could your $3 command be returning a nonzero exit code? You probably
want something more like
touch $2/.$1-begin { eval $3 21 $log ; touch $2/.$1-end }
so your end timestamp always gets created whether or not $3 succeeds.
Also note that in your original script, you only backgrounded touch
$2/.$1-end, which is probably not what you wanted.
This seems not to work - I don't think 'sh' likes nested function braces -
recall that this command appears inside a shell function.
In any case, I think I have nailed the problem. It seems that the
external script being called made reference to 'chown' without explicitly
naming the program's path. Under 'cron' control, there is no path to
/usr/sbin by default so the script was exiting with a non-zero exit status
as several here suggested. Wipes large glob off egg off very red face.
Many thanks to all who took time to answer.
--
Tim Daneliuk [EMAIL PROTECTED]
PGP Key: http://www.tundraware.com/PGP/
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Re: /bin/sh Madness
In the last episode (Feb 17), Tim Daneliuk said:
Dan Nelson wrote:
Could your $3 command be returning a nonzero exit code? You probably
want something more like
touch $2/.$1-begin { eval $3 21 $log ; touch $2/.$1-end }
so your end timestamp always gets created whether or not $3 succeeds.
Also note that in your original script, you only backgrounded touch
$2/.$1-end, which is probably not what you wanted.
This seems not to work - I don't think 'sh' likes nested function
braces - recall that this command appears inside a shell function.
Oops. Braces aren't bourne syntax, and in this case they're the wrong
choice anyway. parens (i.e. a subshell) are what's needed.
touch $2/.$1-begin ( eval $3 21 $log ; touch $2/.$1-end )
I actually tested this one :)
In any case, I think I have nailed the problem. It seems that the
external script being called made reference to 'chown' without explicitly
naming the program's path. Under 'cron' control, there is no path to
/usr/sbin by default so the script was exiting with a non-zero exit
status as several here suggested. Wipes large glob off egg off very
red face.
Many thanks to all who took time to answer.
--
Dan Nelson
[EMAIL PROTECTED]
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/bin/sh Madness
Here is a shell function that behaves quite strangely:
#!/bin/sh
#
# Execute A Command, Noting Start/Stop Time, Logging Output
# Args:
# $1 Command Name
# $2 Log Directory
# $3 Command String To Execute
#
runupd()
{
log=$2/$1.log
timestamp $log
touch $2/.$1-begin eval $3 21 $log touch $2/.$1-end
}
# End of 'runupd()'
So, you might do something like:
runupd freespace /var/log/ df -k
Now, for the weirdness. This function works fine in my script
so long as one of two conditions is met:
1) I run it interactively from the command line (bash)
OR
2) I run it from 'cron' AND $3 is *not* another script
If I try to run it from 'cron' and point $3 to a script, everything gets
run as planned, however, the ending timestamp (touch $2/.$1-end) never
runs. That is, the initial time stamp (.$1-begin) and the command itself
are executed, and output is properly written to the logfile,
but the final timestamp never happens.
I have been fiddling with this on- and off and cannot seem to explain
the behavior. I',m guessing that something about the combination of
'cron'and the 21 $log business is causing the last touch to never
get invoked, but for the life of me, I cannot figure this one out.
Interestingly, this works fine in Linux (SuSE 10.0). In Linux, both
'sh' and 'bash' are the same binary (bash is running as sh). So ..
I went back to FreeBSD (4.x in this case, though the problem is also
noted in 6.x) and changed the SHELL variable in the crontabs file to
use 'bash' - same problem.
This is starting to feel like a problem with file handles getting clobbered
in the FreeBSD exec logic.
Other explanations welcome...
--
Tim Daneliuk [EMAIL PROTECTED]
PGP Key: http://www.tundraware.com/PGP/
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Re: /bin/sh Madness
In the last episode (Feb 16), Tim Daneliuk said:
Here is a shell function that behaves quite strangely:
#!/bin/sh
#
# Execute A Command, Noting Start/Stop Time, Logging Output
# Args:
# $1 Command Name
# $2 Log Directory
# $3 Command String To Execute
#
runupd()
{
log=$2/$1.log
timestamp $log
touch $2/.$1-begin eval $3 21 $log touch $2/.$1-end
}
# End of 'runupd()'
So, you might do something like:
runupd freespace /var/log/ df -k
Now, for the weirdness. This function works fine in my script
so long as one of two conditions is met:
1) I run it interactively from the command line (bash)
OR
2) I run it from 'cron' AND $3 is *not* another script
If I try to run it from 'cron' and point $3 to a script, everything gets
run as planned, however, the ending timestamp (touch $2/.$1-end) never
runs. That is, the initial time stamp (.$1-begin) and the command itself
are executed, and output is properly written to the logfile,
but the final timestamp never happens.
Could your $3 command be returning a nonzero exit code? You probably
want something more like
touch $2/.$1-begin { eval $3 21 $log ; touch $2/.$1-end }
so your end timestamp always gets created whether or not $3 succeeds.
Also note that in your original script, you only backgrounded touch
$2/.$1-end, which is probably not what you wanted.
--
Dan Nelson
[EMAIL PROTECTED]
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