From 2c59f669553677838022d65f2433b31a04bc632d Mon Sep 17 00:00:00 2001 From: Laurent Bercot Date: Tue, 5 May 2015 13:10:13 +0000 Subject: - add trap - rc for 2.1.2.0 --- doc/trap.html | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+) create mode 100644 doc/trap.html (limited to 'doc/trap.html') diff --git a/doc/trap.html b/doc/trap.html new file mode 100644 index 0000000..ff03c2e --- /dev/null +++ b/doc/trap.html @@ -0,0 +1,98 @@ + + + + + execline: the trap command + + + + + + +

+execline
+Software
+skarnet.org +

+ +

The `trap` program

+ +trap traps signals and runs a variety of commands according +to the signals it catches. + +

Interface

+ +

+ In an execlineb script: +

+ +

+     trap [ -x ] [ -t millisecs ]
+     {
+       [ timeout { progtimeout... } ]
+       [ SIGTERM { progsigterm... } ]
+       [ quit { progsigquit... } ]
+       [ 1 { progsighup... } ]
+       ...
+     }
+     prog...
+

+ +

trap reads a sequence of directives in a +block. It expects at least one +directive.
Each directive is a keyword followed by a block.
The keyword can be the special word timeout, a signal +name (case-insensitive, with or without the SIG prefix), + or a signal number. The block following it is a command line to +run when the specified event occurs.
trap sets traps for the various directives it reads. +A trap for SIGTERM will be triggered when the trap +program receives a SIGTERM. +A trap for timeout will be triggered when millisecs +milliseconds elapse without a signal being caught.
It spawns a child executing prog....
It sets the ! environment +variable to the pid of the prog... process.
Whenever it catches a signal, it spawns the program described in the +corresponding directive. It will not spawn a program for the same signal +twice: if the first subprocess is still active when another instance of the +same signal arrives, this second instance is ignored.
When prog... exits, trap exits with an +approximation of the same exit code.

+ +

Options

+ +

-x : forward signals. If this option is given, +any signal that trap receives and that is not explicitly +trapped will be sent to prog. By default, trap does +not forward any signals, and does not ignore them either - for instance a +SIGTERM, unless caught by a SIGTERM directive, will kill the +trap process (and leave prog running). With the +-x option, without a SIGTERM directive, a SIGTERM +will be still be caught by trap, that will send it to +prog.
-t millisecs : if a timeout +directive exists, the corresponding progtimeout... will be run +every time millisecs milliseconds elapse without trap +receiving a signal. By default, millisecs is 0, which means +infinite (i.e. a timeout directive will never trigger).

+ +

Notes

+ +

Programs defined in command line directives can start with +import ! to retrieve the pid of +prog in ${!}
trap is a standard shell builtin, with similar +functionality. It is more idiomatic, and probably more efficient, +to use that builtin in shell scripts, and to only use the +trap program in execline scripts.

+ + + -- cgit v1.2.3

The trap program

Interface

Options

Notes

The `trap` program