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Diffstat (limited to 'doc/trap.html')
| -rw-r--r-- | doc/trap.html | 25 |
1 files changed, 12 insertions, 13 deletions
diff --git a/doc/trap.html b/doc/trap.html index 03d5bc4..fafd5c7 100644 --- a/doc/trap.html +++ b/doc/trap.html @@ -28,12 +28,12 @@ to the signals it catches. </p> <pre> - trap [ -x ] [ -t <em>millisecs</em> ] + trap [ -x ] { - [ timeout { <em>progtimeout...</em> } ] [ SIGTERM { <em>progsigterm...</em> } ] [ quit { <em>progsigquit...</em> } ] [ 1 { <em>progsighup</em>... } ] + [ default { <em>progdefault</em>... } ] ... } <em>prog...</em> @@ -50,12 +50,12 @@ name (case-insensitive, with or without the <tt>SIG</tt> prefix), run when the specified event occurs. </li> <li> <tt>trap</tt> sets traps for the various directives it reads. A trap for <tt>SIGTERM</tt> will be triggered when the <tt>trap</tt> -program receives a SIGTERM. -A trap for <tt>timeout</tt> will be triggered when <em>millisecs</em> -milliseconds elapse without a signal being caught. </li> +program receives a SIGTERM. A <tt>default</tt> +trap will be used for any signal that is not caught by another trap. </li> <li> It spawns a child executing <em>prog...</em>. </li> <li> It sets the <tt>!</tt> environment -variable to the pid of the <em>prog...</em> process. </li> +variable to the pid of the <em>prog...</em> process, and the <tt>SIGNAL</tt> +environment variable to the trapped signal. </li> <li> 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 @@ -75,12 +75,8 @@ SIGTERM, unless caught by a <tt>SIGTERM</tt> directive, will kill the <tt>trap</tt> process (and leave <em>prog</em> running). With the <tt>-x</tt> option, without a <tt>SIGTERM</tt> directive, a SIGTERM will be still be caught by <tt>trap</tt>, that will send it to -<em>prog</em>. </li> - <li> <tt>-t <em>millisecs</em></tt> : if a <tt>timeout</tt> -directive exists, the corresponding <em>progtimeout...</em> will be run -every time <em>millisecs</em> milliseconds elapse without <tt>trap</tt> -receiving a signal. By default, <em>millisecs</em> is 0, which means -infinite (i.e. a <tt>timeout</tt> directive will never trigger). </li> +<em>prog</em>. Note that if a <tt>default</tt> directive is present, +this option does nothing. </li> </ul> <h2> Notes </h2> @@ -88,7 +84,10 @@ infinite (i.e. a <tt>timeout</tt> directive will never trigger). </li> <ul> <li> Programs defined in command line directives can start with <tt><a href="importas.html">importas</a> ! !</tt> to retrieve the pid of -<em>prog</em> in <tt>${!}</tt> </li> +<em>prog</em> in <tt>$!</tt>. If they need the signal number, which +can be the case in <tt>default</tt> directives, they can for instance use +<tt><a href="multisubstitute.html">multisubstitute</a> { importas ! ! importas SIGNAL SIGNAL }</tt> +to get both <tt>$!</tt> and <tt>$SIGNAL</tt> substitutions. </li> <li> <tt>trap</tt> 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 |