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Full Discussion: Find null fields in file
Top Forums Shell Programming and Scripting Find null fields in file Post 302077519 by blowtorch on Thursday 22nd of June 2006 10:09:03 PM
Old 06-22-2006
How do you know that a field is empty? Would there be just two commas following each other? Something like this?
Code:
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17...
1,2,3,4,5,6,7,8,9,10,11,12,13,,15,16,17...
1,2,3,4,5,6,7,8,9,10,11,12,13,,15,,17...

Note that the fourteenth field is empty in the second and the third line, while the sixteenth field is empty in the third line.
If so, then you can just use the command that you've used.
Code:
bash-3.00$ cat test
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17
1,2,3,4,5,6,7,8,9,10,11,12,13,,15,16,17
1,2,3,4,5,6,7,8,9,10,11,12,13,,15,,17
bash-3.00$ cat test.sh
#!/usr/bin/ksh
oldIFS=$IFS
IFS=$IFS,
export IFS
cut -d',' -f14,16 test|while read fourteen sixteen; do
        echo fourteen: $fourteen sixteen: $sixteen
        [[ -z "$fourteen" ]] && echo fourteenth field is blank
        [[ -z "$sixteen" ]] && echo sixteenth field is blank
done

 

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LEARN ABOUT ULTRIX

trace

trace(1)						      General Commands Manual							  trace(1)

Name
       trace - trace system calls of programs

Syntax
       trace [options] cmd args...

Description
       The  command  with  no flag arguments traces for the given cmd and args all system calls made and prints a time stamp, the PID, call and/or
       return values and arguments and puts its output in the file trace.dump.

Options
       -f filename
	       Puts dump in file filename.

       -z      Echos arguments only.

       Only one of the following option arguments can be specified at one time.

       -c#     Traces given PIDs and their children.  Up to sixteen PIDs can be specified.

       -g#     Traces given groups only.  Up to sixteen Group IDs can be specified.

       -p#     Traces given PIDs only.	Up to sixteen PIDs can be specified.

       -s#     Traces given system calls only.	Up to sixteen PIDs can be specified.

       -u#     Traces given UIDs only.	Up to sixteen PIDs can be specified.

Examples
       trace -f ls.dump ls -l /dev >ls.out
       runs the cmd ls -l /dev and puts the trace in ls.dump and output in ls.out.
       trace -f csh.trace -p $$ &
       will trace your login shell in the background. To stop the trace just send it a termination signal (that is, kill -TERM trace_pid).

Restrictions
       Due to security, no one, not even the super-user can trace anyone else's programs. This sort of negates some of the usefulness  of  the	-g
       and -u flags.

       The program cannot be traced.

       Only 16 numbers can be given to the -c, -p, -g, -u, and -s flags.

       The kernel configuration file must contain the following:
       options	       SYS_TRACE
       pseudo-device   sys_trace

       In addition, the superuser must use the following command sequence to create the device:
       cd /dev
       MAKEDEV trace
       If both lines are not in the configuration file or if the device is not made, the message "Cannot open /dev/trace" appears.

Files
       /dev/trace     read only character special device for reading syscall data.

       trace.dump     default file for the system call trace data.

See Also
       open(2), close(2), ioctl(2), select(2), read(2), trace(5)

																	  trace(1)
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