如何腳本表示什么意思？

oceanmeng

1. #!/usr/bin/sh
   
2. trap "exit" 2 3
   
3. trap "exit" 1

復制代碼

wenhq

trap [-lp] [[arg] sigspec ...]
              The command arg is to be read and executed when the shell receives signal(s) sigspec.  If arg is absent (and there is a single sigspec) or -,  each specified  signal  is reset to its original disposition (the value it had upon entrance to the shell).  If arg is the null string the signal speci-fied by each sigspec is ignored by the shell and by the commands it invokes.  If arg is not present and -p has been supplied, then  the  trap  commands associated with each sigspec are displayed.  If no arguments are supplied or if only -p is given, trap prints the list of commands associated with each signal.  The -l option causes the shell to print a list of signal names and their corresponding numbers.  Each sigspec is either a signal name defined in <signal.h>, or a signal number.  Signal names are case insensitive and the SIG prefix is optional.

              If  a sigspec is EXIT (0) the command arg is executed on exit from the shell.  If a sigspec is DEBUG, the command arg is executed before every simple command, for command, case command, select command, every arithmetic for command, and before the first command executes  in  a  shell  function (see SHELL GRAMMAR above).  Refer to the description of the extdebug option to the shopt builtin for details of its effect on the DEBUG trap.  If a sigspec is RETURN, the command arg is executed each time a shell function or a script executed with the . or source builtins finishes executing.

              If a sigspec is ERR, the command arg is executed whenever a simple command has a non-zero exit status, subject to the  following  conditions.   The ERR  trap  is not executed if the failed command is part of the command list immediately following a while or until keyword, part of the test in an
              if statement, part of a command executed in a && or ?.. list, or if the command?. return value is being inverted via !.  These are the  same  conditions obeyed by the errexit option.

              Signals  ignored upon entry to the shell cannot be trapped or reset.  Trapped signals that are not being ignored are reset to their original values in a subshell or subshell environment when one is created.  The return status is false if any sigspec is invalid; otherwise trap returns true.