trap(1)                                                            User Commands                                                           trap(1)

NAME

       trap, onintr - shell built-in functions to respond to (hardware) signals

SYNOPSIS

   sh
       trap [ argument n [n2...]]

   csh
       onintr [-| label]

   ksh
       *trap [ arg sig [ sig2...]]

DESCRIPTION

   sh
       The  trap command argument is to be read and executed when the shell receives numeric or symbolic signal(s) (n). (Note: argument is scanned
       once when the trap is set and once when the trap is taken.) Trap commands are executed in order of signal number or corresponding  symbolic
       names. Any attempt to set a trap on a signal that was ignored on entry to the current shell is ineffective. An attempt to trap on signal 11
       (memory fault) produces an error. If argument is absent all trap(s) n are reset to their original values. If argument is  the  null  string
       this  signal is ignored by the shell and by the commands it invokes. If n is 0 the command argument is executed on exit from the shell. The
       trap command with no arguments prints a list of commands associated with each signal number.

   csh
       onintr controls the action of the shell on interrupts. With no arguments, onintr restores the default action of the  shell  on  interrupts.
       (The  shell  terminates  shell  scripts and returns to the terminal command input level). With the - argument, the shell ignores all inter-
       rupts. With a label argument, the shell executes a goto label when an interrupt is received or a child process terminates  because  it  was
       interrupted.

   ksh
       trap  uses  arg as a command to be read and executed when the shell receives signal(s) sig. (Note that arg is scanned once when the trap is
       set and once when the trap is taken.) Each sig can be given as a number or as the name of the signal. trap commands are executed  in  order
       of  signal  number. Any attempt to set a trap on a signal that was ignored on entry to the current shell is ineffective.  If arg is omitted
       or is -, then the trap(s) for each sig are reset to their original values.  If arg is the null (the empty string, e.g., ""  )  string  then
       this  signal is ignored by the shell and by the commands it invokes.  If sig is ERR then arg will be executed whenever a command has a non-
       zero exit status.  If sig is DEBUG then arg will be executed after each command. If sig is 0 or EXIT for a trap set  outside  any  function
       then the command arg is executed on exit from the shell.  The trap command with no arguments prints a list of commands associated with each
       signal number.

       On this man page, ksh(1) commands that are preceded by one or two * (asterisks) are treated specially in the following ways:

       1.  Variable assignment lists preceding the command remain in effect when the command completes.

       2.  I/O redirections are processed after variable assignments.

       3.  Errors cause a script that contains them to abort.

       4.  Words, following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a  vari-
           able  assignment.  This means that tilde substitution is performed after the = sign and word splitting and file name generation are not
           performed.

ATTRIBUTES

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

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE         |      ATTRIBUTE VALUE        |
       +-----------------------------+-----------------------------+
       |Availability                 |SUNWcsu                      |
       +-----------------------------+-----------------------------+

SEE ALSO

       csh(1), exit(1), ksh(1), sh(1), attributes(5)

SunOS 5.10                                                          23 Oct 1994                                                            trap(1)