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trap(1)                          User Commands                         trap(1)



NAME
       trap,  onintr  - shell built-in functions to respond to (hardware) sig-
       nals

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  com-
       mands  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 argu-
       ments, 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  interrupts.
       With  a  label argument, the shell executes a goto label when an inter-
       rupt is received or a child process terminates because  it  was  inter-
       rupted.

   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  sig-
       nal  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  com-
       mand  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:


       tab()    allbox;    cw(2.750000i)|     cw(2.750000i)     lw(2.750000i)|
       lw(2.750000i).  ATTRIBUTE TYPEATTRIBUTE VALUE AvailabilitySUNWcsu


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




SunOS 5.10                        23 Oct 1994                          trap(1)