150479Speter$FreeBSD: releng/11.0/usr.sbin/cron/doc/FEATURES 50479 1999-08-28 01:35:59Z peter $ 22311Sjkh 32311SjkhFeatures of Vixie's cron relative to BSD 4.[23] and SysV crons: 42311Sjkh 52311Sjkh-- Environment variables can be set in each crontab. SHELL, USER, 62311Sjkh LOGNAME, and HOME are set from the user's passwd entry; all except 72311Sjkh USER can be changed in the crontab. PATH is especially useful to 82311Sjkh set there. TZ can be set, but cron ignores it other than passing 92311Sjkh it on through to the commands it runs. Format is 102311Sjkh 112311Sjkh variable=value 122311Sjkh 132311Sjkh Blanks surrounding the '=' will be eaten; other blanks in value are 142311Sjkh okay. Leading or trailing blanks can be preserved by quoting, single 152311Sjkh or double quotes are okay, just so they match. 162311Sjkh 172311Sjkh PATH=.:/bin:/usr/bin 182311Sjkh SHELL=/bin/sh 192311Sjkh FOOBAR = this is a long blanky example 202311Sjkh 212311Sjkh Above, FOOBAR would get "this is a long blanky example" as its value. 222311Sjkh 232311Sjkh SHELL and HOME will be used when it's time to run a command; if 242311Sjkh you don't set them, HOME defaults to your /etc/passwd entry 252311Sjkh and SHELL defaults to /bin/sh. 262311Sjkh 272311Sjkh MAILTO, if set to the login name of a user on your system, will be the 282311Sjkh person that cron mails the output of commands in that crontab. This is 292311Sjkh useful if you decide on BINMAIL when configuring cron.h, since binmail 302311Sjkh doesn't know anything about aliasing. 312311Sjkh 322311Sjkh-- Weekdays can be specified by name. Case is not significant, but only 332311Sjkh the first three letters should be specified. 342311Sjkh 352311Sjkh-- Months can likewise be specified by name. Three letters only. 362311Sjkh 372311Sjkh-- Ranges and lists can be mixed. Standard crons won't allow '1,3-5'. 382311Sjkh 392311Sjkh-- Ranges can specify 'step' values. '10-16/2' is like '10,12,14,16'. 402311Sjkh 412311Sjkh-- Sunday is both day 0 and day 7 -- apparently BSD and ATT disagree 422311Sjkh about this. 432311Sjkh 442311Sjkh-- Each user gets their own crontab file. This is a win over BSD 4.2, 452311Sjkh where only root has one, and over BSD 4.3, where they made the crontab 462311Sjkh format incompatible and although the commands can be run by non-root 472311Sjkh uid's, root is still the only one who can edit the crontab file. This 482311Sjkh feature mimics the SysV cron. 492311Sjkh 502311Sjkh-- The 'crontab' command is loosely compatible with SysV, but has more 512311Sjkh options which just generally make more sense. Running crontab with 522311Sjkh no arguments will print a cute little summary of the command syntax. 532311Sjkh 542311Sjkh-- Comments and blank lines are allowed in the crontab file. Comments 552311Sjkh must be on a line by themselves; leading whitespace is ignored, and 562311Sjkh a '#' introduces the comment. 572311Sjkh 582311Sjkh-- (big win) If the `crontab' command changes anything in any crontab, 592311Sjkh the 'cron' daemon will reload all the tables before running the 602311Sjkh next iteration. In some crons, you have to kill and restart the 612311Sjkh daemon whenever you change a crontab. In other crons, the crontab 622311Sjkh file is reread and reparsed every minute even if it didn't change. 632311Sjkh 642311Sjkh-- In order to support the automatic reload, the crontab files are not 652311Sjkh readable or writable except by 'crontab' or 'cron'. This is not a 662311Sjkh problem, since 'crontab' will let you do pretty much whatever you 672311Sjkh want to your own crontab, or if you are root, to anybody's crontab. 682311Sjkh 692311Sjkh-- If any output is generated by a command (on stdout OR stderr), it will 702311Sjkh be mailed to the owner of the crontab that contained the command (or 712311Sjkh MAILTO, see discussion of environment variables, above). The headers 722311Sjkh of the mail message will include the command that was run, and a 732311Sjkh complete list of the environment that was passed to it, which will 742311Sjkh contain (at least) the USER (LOGNAME on SysV), HOME, and SHELL. 752311Sjkh 762311Sjkh-- the dom/dow situation is odd. '* * 1,15 * Sun' will run on the 772311Sjkh first and fifteenth AND every Sunday; '* * * * Sun' will run *only* 782311Sjkh on Sundays; '* * 1,15 * *' will run *only* the 1st and 15th. this 792311Sjkh is why we keep 'e->dow_star' and 'e->dom_star'. I didn't think up 802311Sjkh this behaviour; it's how cron has always worked but the documentation 812311Sjkh hasn't been very clear. I have been told that some AT&T crons do not 822311Sjkh act this way and do the more reasonable thing, which is (IMHO) to "or" 832311Sjkh the various field-matches together. In that sense this cron may not 842311Sjkh be completely similar to some AT&T crons. 85