X-Git-Url: http://git.annexia.org/?p=whenjobs.git;a=blobdiff_plain;f=tools%2Fwhenjobs.pod;h=b8c76a6c6637f2a8c4bc319032ce4bf864234225;hp=2acec9f96c554b262e77a8f65c14fce0399e4b0b;hb=545581eb916ac5f020295b59458e16af51ea6cc5;hpb=600c8000490fa8279b23ce866e9ecc2a90e5f79a diff --git a/tools/whenjobs.pod b/tools/whenjobs.pod index 2acec9f..b8c76a6 100644 --- a/tools/whenjobs.pod +++ b/tools/whenjobs.pod @@ -24,6 +24,12 @@ Start and stop the per-user daemon: whenjobs --daemon-status whenjobs --daemon-restart +Examine running jobs: + + whenjobs --jobs + whenjobs --cancel serial + whenjobs --start "name" + =head1 DESCRIPTION Whenjobs is a powerful but simple replacement for cron. It lets you @@ -83,6 +89,14 @@ The act of setting a variable (using I<--set>) can trigger jobs to run. =over 4 +=item B<--cancel> serial + +Cancel the job with the given serial number. + +Use I<--jobs> to list running jobs along with their serial numbers. +The serial number is also available in the job script (as +C<$JOBSERIAL>) and in the log file. + =item B<--daemon-start> =item B<--daemon-stop> @@ -112,6 +126,13 @@ C is used. Print the value of a variable. +=item B<--jobs> + +List all running jobs. + +Note that it is possible for the same job to be running more than once +(for example, a periodic job that takes longer than the period to run). + =item B<-l> =item B<--list> @@ -128,6 +149,13 @@ source, eg: whenjobs --lib $builddir/lib -e +=item B<--start> "job name" + +Start the job immediately and unconditionally. + +This runs the job even if its normal preconditions are not met. This +may cause unexpected results, so use with caution. + =item B<--set> variable value =item B<--type> bool|int|float|string|unit @@ -396,14 +424,18 @@ ran, then this evaluates to true, else false. This is the same as writing C variable>. -B There is a subtle and difficult problem with using the -I operator: The first time the expression is evaluated, the -job has (by definition) not yet run. Therefore C -evaluates to C<""> (see definition of I above). Since -C<"" E everything>, the I operator evaluates to -false, and since this usually means the job does not run, the -operator always evaluates to false. A future version of whenjobs -will address this problem. +B There is a subtle gotcha with the I operator: The +first time the expression is evaluated, the job has (by definition) +not yet run. Therefore C evaluates to C<""> (see +definition of I above). Since it is always true that + + "" < anything + +the I operator evaluates to false, and since this usually +means the job does not run, the operator always evaluates to false. + +To fix this, ensure that the variable is initialized (see +L below). =item B @@ -411,9 +443,7 @@ This evaluates to true the first time the expression is evaluated after the jobs file has been reloaded or the daemon restarted. Thereafter it evaluates to false. -You can use this to initialize variables, but note that this does not -solve the I operator problem described above, because -variables are initialized too late to affect that. +Don't use this to initialize variables: it won't do what you mean. =item B @@ -513,12 +543,165 @@ with C: The job name is passed to the shell script in the C<$JOBNAME> environment variable. +=head2 OCAML EXPRESSIONS + +As well as simple "every" and "when" expressions, advanced users may +want to use arbitrary OCaml expressions, functions, etc in the jobs +script. These are useful for factoring common code or strings, for +setting the initial values of variables, or for defining pre and post +functions. + +A simple example of an OCaml expression is: + + let prefix = "daily_" + + job (prefix ^ "virus_scan") + every day : + << + # ... + >> + + job (prefix ^ "disk_check") + every day : + << + # ... + >> + +which creates two jobs called C<"daily_virus_scan"> and +C<"daily_disk_check"> (C<^> is the OCaml string concatenation +operator). + +OCaml expressions have access to a library of functions called +B which is described below. It lets you set variables, +create jobs algorithmically, etc. + +The OCaml expressions run once, when the jobs file is being loaded or +reloaded. + +=head3 SETTING THE INITIAL VALUE OF VARIABLES + +Variables are created when they are referenced, and until set they +have the value empty string (just like the shell). Across file +reloads, the previous values of variables are preserved. + +To initialize a variable to a known value when the jobs file is +loaded, call one of the C functions as in +this example: + + let () = + Whentools.set_variable "name" "Richard"; + Whentools.set_variable_int "counter" 0 + +=head3 POST FUNCTIONS + +After a job runs, you can control what happens to its output by +writing a C function. To write a post function you have to +name the job (ie. have an explicit C statement). Put C +after the job name like this: + + job "poll source" + post (Whentools.mailto "you@example.com") + every 10 seconds : + << + # ... + >> + +A number of post functions are available in the library; see below. + +You can also write your own post functions (in OCaml). The +function is passed one argument which is a C struct, +defined below. + +=head3 WHENTOOLS LIBRARY + +=head4 Functions + +=over 4 + +=item B [I<~only_on_failure:true>] +[I<~from:from_address>] I I + +This built-in post function sends the result of the script by email to +the given email address. + +If the optional C<~only_on_failure:true> flag is set, then it is only +sent out if the script failed. + +If the optional C<~from> flag is set, then the from address is set +accordingly. This is sometimes needed when sending mail. + +Note the C parameter is passed implicitly by the daemon. You +do not need to add it. + +Here are some examples of using the mailto function: + + job "ex.1" + post (Whentools.mailto "you@example.com") + every 10 seconds : + << + # do something + >> + + job "ex.2" + post (Whentools.mailto ~only_on_failure:true + "you@example.com") + every 10 seconds : + << + # do something + >> + + let from = "me@example.com" + let to_addr = "you@example.com" + + job "ex.3" + post (Whentools.mailto ~from to_addr) + every 10 seconds : + << + # do something + >> + +=item B I I + +Set variable I to the string. + +=item B I I + +Set variable I to the boolean value I. + +=item B I I +Set variable I to the integer value I. +=item B I I +Set variable I to the string value . This is +the same as I. +=item B I I +Set variable I to the floating point value I. +=back + +=head4 Structures + +=over 4 + +=item B + +This structure is passed to post functions. It has the following +fields: + + type result = { + res_job_name : string; # job name + res_serial : big_int; # job serial (same as $JOBSERIAL) + res_code : int; # return code from the shell script + res_tmpdir : string; # temporary directory script ran in + res_output : string; # filename of stdout/stderr output + res_start_time : float; # when the job started + } + +=back =head1 FILES