Reg trap signals Post: 302855937

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Top Forums Shell Programming and Scripting Reg trap signals Post 302855937 by Don Cragun on Saturday 21st of September 2013 04:11:40 PM

09-21-2013

Registered User

In recent versions of ksh, trap action DEBUG causes action to be executed just before each simple command the shell executes after that until the trap is removed. The DEBUG trap action is not inherited by subshells nor in functions. To get a better view of what is going on, you might want to try the following modification of your code:

Code:

#!/bin/ksh
let LIMIT=50
function check {
        printf "In check: %s\n" "${.sh.command}"
        if [[ LIMIT -eq 50 ]]
        then    print LIMIT OK
        else    print "LIMIT changed!"
        fi
} 
echo 1
trap check DEBUG
echo 2
print $LIMIT
if [ $LIMIT -gt 40 ]
then    echo 3t
else    echo 3f
fi
LIMIT=$((LIMIT + 30))
echo 4
trap - DEBUG
echo 5

Note that the compound variable .sh.command is the command that is about to be executed. The above script produces:

Code:

1
In check: echo 2
LIMIT OK
2
In check: print 50
LIMIT OK
50
In check: '[' 50 -gt 40 ']'
LIMIT OK
In check: echo 3t
LIMIT OK
3t
In check: LIMIT=80
LIMIT changed!
In check: echo 4
LIMIT changed!
4
In check: trap - DEBUG
LIMIT changed!
5

Last edited by Don Cragun; 09-21-2013 at 05:19 PM.. Reason: Fix typo

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LEARN ABOUT OPENSOLARIS

gcmp

CMP(1)								   User Commands							    CMP(1)

NAME

       cmp - compare two files byte by byte

SYNOPSIS

       cmp [OPTION]... FILE1 [FILE2 [SKIP1 [SKIP2]]]

DESCRIPTION

       Compare two files byte by byte.

       -b  --print-bytes
	      Print differing bytes.

       -i SKIP	--ignore-initial=SKIP
	      Skip the first SKIP bytes of input.

       -i SKIP1:SKIP2  --ignore-initial=SKIP1:SKIP2

	      Skip the first SKIP1 bytes of FILE1 and the first SKIP2 bytes of FILE2.

       -l  --verbose
	      Output byte numbers and values of all differing bytes.

       -n LIMIT  --bytes=LIMIT
	      Compare at most LIMIT bytes.

       -s  --quiet  --silent
	      Output nothing; yield exit status only.

       -v  --version
	      Output version info.

       --help Output this help.

       SKIP1  and  SKIP2  are  the number of bytes to skip in each file.  SKIP values may be followed by the following multiplicative suffixes: kB
       1000, K 1024, MB 1,000,000, M 1,048,576, GB 1,000,000,000, G 1,073,741,824, and so on for T, P, E, Z, Y.

       If a FILE is `-' or missing, read standard input.

AUTHOR

       Written by Torbjorn Granlund and David MacKenzie.

REPORTING BUGS

       Report bugs to <bug-gnu-utils@gnu.org>.

COPYRIGHT

       Copyright (C) 2002 Free Software Foundation, Inc.

       This program comes with NO WARRANTY, to the extent permitted by law.  You may redistribute copies of this program under the  terms  of  the
       GNU General Public License.  For more information about these matters, see the file named COPYING.

SEE ALSO

       The  full  documentation  for cmp is maintained as a Texinfo manual.  If the info and cmp programs are properly installed at your site, the
       command

	      info diff

       should give you access to the complete manual.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +--------------------+-------------------+
       |  ATTRIBUTE TYPE    |  ATTRIBUTE VALUE	|
       +--------------------+-------------------+
       |Availability	    | SUNWgnu-diffutils |
       +--------------------+-------------------+
       |Interface Stability | Uncommitted	|
       +--------------------+-------------------+
NOTES

       Source for GNU diffutils is available on http://opensolaris.org.

diffutils 2.8.1 						    April 2002								    CMP(1)