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Full Discussion: Need program to continue even when encountering errors
Top Forums Programming Need program to continue even when encountering errors Post 302852265 by jim mcnamara on Wednesday 11th of September 2013 05:52:37 AM
Old 09-11-2013
It is almost always illogical to continue after not finding a data file. What are you planning to do? Make up defaults - like setting defaults in the absence of data.

A lot of applications will ignore the absence of/or an empty config file, but the application has reasonable defaults defined. This kind of thing- checking defaults - is done when the program starts.

If you are having issues with a long-running program aborting on file not found, consider using a system call like access() to enumerate all required file resources when the program starts. Instead of running for 5 minutes, then aborting.

You do not have to open a file to see if you can read or write to it.

You simply cannot process application data from a file if it is not there. Or permissions are wrong. Or because you don't want a 3:00am telephone call. The program has to abort. Period.

Other kinds of resources may go offline - like a tape drive - then be brought back online or mounted with the correct tape. You can, again, at the get-go enumerate resources, then tell the person running the report to mount the right tape.

For report programs, a huge percent of the lines of code often deal with checking parameters and resources, getting usernames and passwords, etc. The other 10% or so actually processes data. You have to do a ton of upfront work before trying to run the actual report code. This is true for lots of different kinds of apps.

The way your question is stated it is not clear.
Last edited by jim mcnamara; 09-11-2013 at 06:58 AM..
 

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LEARN ABOUT CENTOS

tapeinfo

TAPEINFO(1)						      General Commands Manual						       TAPEINFO(1)

NAME

       tapeinfo - report SCSI tape device info

SYNOPSIS

       tapeinfo -f <scsi-generic-device>

DESCRIPTION

       The  tapeinfo  command  reads  various information from SCSI tape drives that is not generally available via most vendors' tape drivers. It
       issues raw commands directly to the tape drive, using either the  operating  system's  SCSI  generic  device  (	e.g.  /dev/sg0	on  Linux,
       /dev/pass0 on FreeBSD) or the raw SCSI I/O ioctl on a tape device on some operating systems.

       One  good  time	to  use 'tapeinfo' is immediately after a tape i/o operation has failed. On tape drives that support HP's 'tapealert' API,
       'tapeinfo' will report a more exact description of what went wrong.

       Do be aware that 'tapeinfo' is not a substitute for your operating system's own 'mt' or similar tape driver control program. It is intended
       to supplement, not replace, programs like 'mt' that access your operating system's tape driver in order to report or set information.

OPTIONS

       The first argument, given following -f , is the SCSI generic device corresponding to your tape drive.  Consult your operating system's doc-
       umentation for more information (for example, under Linux these are generally start at /dev/sg0 under FreeBSD these start at /dev/pass0).

       Under FreeBSD, 'camcontrol devlist' will tell you what SCSI devices you have, along with which 'pass' device controls  them.  Under  Linux,
       "cat /proc/scsi/scsi" will tell you what SCSI devices you have.

BUGS AND LIMITATIONS

       This program has only been tested on Linux with a limited number of tape drives (HP DDS4, Seagate AIT).

AVAILABILITY

       tapeinfo  is  currently	being maintained by Robert Nelson <robertnelson@users.sourceforge.net> as part of the 'mtx' suite of programs. The
       'mtx' home page is http://mtx.sourceforge.net  and  the	actual	code  is  currently  available	there  and  via  SVN  from  http://source-
       forge.net/projects/mtx.

SEE ALSO

       mt(1),mtx(1),scsitape(1),scsieject(1),loaderinfo(1)

								    TAPEINFO1.0 						       TAPEINFO(1)
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