TRAPPING SIGNALS IN CSH

[Christopher J. Hawley]

    In article <9104242103.AA11863 at ccfiris.aedc>, mcdonald at AEDC-VAX.AF.MIL
writes:

|>            My problem arises when the user hits Ctrl-C when he first logs
|> in which kills the execution of /etc/cshrc, thus my expiration checker does
|> not get executed.  How can I trap these signals in a csh?

    Read the description of the csh builtin command "onintr" in  csh(1) .
It provides a barely adequate (IMHO) means of intercepting interrupt signals;
used in conjunction with some  stty(1)  contortions to disable other signals
from the keyboard, you could write something similar to the following:

		    ...
		# Assume we're executing from a tty.
		# Save tty settings, disable signals except for SIGINT
		set ottymode = `stty -g`
		stty  quit '^-'			# "undef" on some BSD systems
		# Trap interrupts to clean-up portion of script
		onintr interrupted
		    ...
		  <commands to change password>
		    ...
		goto finished

		# Clean-up handling (executed when interrupted)
		interrupted:
		    ...
		  <commands to undo partial changes, set return status>
		    ...

		# Here to complete task, restore terminal modes, return status.
		# Restore original tty settings
		stty  $ottymode; unset ottymode
		# Revert to previous interrupt handling (if sourced inline)
		onintr
		# Exit with return status (if subshell or aborted)
		exit($returnstatus)

|> In a Bourne shell all I have to do is trap them with the trap command.

    Y'know, that's probably the easiest way to accomplish the task...
use an explicit invocation:

		/bin/sh  chgpwdscript

Use the  trap  builtin and set  SHELL=/bin/sh  within  chgpwdscript .

|>   | Kenneth M. McDonald * OAO Corp * Arnold Engineering Development Center |
|>   |          MS 120 * Arnold AFS, TN 37389-9998 * (615) 454-3413           |

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---
    Christopher J. Hawley / esper               chawley at sundiver.esd.sgi.com
    Silicon Graphics, Inc.    1L-945            phone:  415 / 335-1621
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