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spirit posteets tagged cron

 

  • Preventing Cron Job Collision
    6 years ago
    Prevents jobs to collide if they take longer to run than the frequency itself
    1. $fp = fopen(‘/tmp/lock.txt’, ‘r+’);
    3. if(!flock($fp, LOCK_EX | LOCK_NB)) {
    4.    echo ‘Unable to obtain lock’;
    5.    exit(-1);
    6. }
    8. /* … */
    10. fclose($fp);
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  • Blocking Web Access to Cron Jobs
    6 years ago
    it’s also possibl with a .htaccess file and “deny from all ” in that file
    1. if (isset($_SERVER[‘REMOTE_ADDR’])) die(‘Permission denied.’);
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  • onlogdo – monitor a log file and execute commands based on patterns 
    7 years ago
    # onlogdo: a hack to handle a common problem: when a certain message shows up in the log file, an action should be performed. (credits to Ben Wong)
    1. #!/bin/bash
    3. # Author: Ben Wong <ben@wongs.net>
    4. # Created on: <2001-08-08 11:56:03 hackerb9>
    5. # Time-stamp: <2002-11-20 14:13:11 bbb>
    7. # onlogdo: a hack to handle a common problem: when a certain message
    8. # shows up in the log file, an action should be performed. E.g.: when
    9. # a PC-card network device is inserted, it should be ifconfig’d or
    10. # perhaps dhclient should be run. This program can do that in a fairly
    11. # reasonable way.
    15. ### FIRST, THE HELPER FUNCTIONS ###
    17. function showmanpage () {
    18.     cat <<‘EOF’
    19. NAME
    21.    onlogdo – monitor a log file and execute commands based on patterns
    24. SYNOPSIS
    26.    onlogdo <logfile> <pattern> <command> [ <pattern> <command> … ]
    28.      logfile: a file that gets appended to (e.g., /var/log/messages),
    29.      pattern: a string (can use bash‘s extended pathname globbing syntax),
    30.      command: the command to run when the previous pattern is seen.
    33. DESCRIPTION
    35.     Onlogdo is a hack to handle a common problem: when a certain
    36.     message shows up in a log file, an action should be performed.
    37.     E.g.: when a PC-card network device is inserted, it should be
    38.     ifconfig’d or perhaps dhclient should be run. This program can do
    39.     that in a fairly reasonable way.
    41.     Onlogdo continuously reads lines as they are appended to a log
    42.     file. When a line matches a given pattern, the command associated
    43.     with that pattern is run in the background. The patterns
    44.     recognized are standard pathname globbing (*, ?, []) plus bash‘s
    45.     extended pattern matching (extglob) syntax (see bash(1)).
    47.     The log file is reopened properly, if the log file being read is
    48.     rotated. Also, since it blocks when waiting for new lines, onlogdo
    49.     takes up almost no CPU time.
    52. PATTERN MATCHING SYNTAX
    54.     Don’t worry about learning the pattern matching the first time you
    55.     read this manual; you‘ll rarely need it, unless you’re anal about
    56.     being as succinct as possible. (Like the author).
    58.     The following is an excerpt from bash‘s man page; see bash(1) for
    59.     full details. In the following description, a pattern-list is a
    60.     list of one or more patterns separated by a |. Composite patterns
    61.     may be formed using one or more of the following sub-patterns:
    63.        *      Matches any string, including the null string.
    65.        ?      Matches any single character.
    67.        […]  Matches any one of the enclosed characters. A pair of
    68.               characters separated by a hyphen denotes a range
    69.               expression. If the first character following the [ is a
    70.               ! or a ^ then any character not enclosed is matched.
    72.       ?(pattern-list)
    73.              Matches zero or one occurrence of the  given patterns
    74.       *(pattern-list)
    75.              Matches  zero  or  more  occurrences  of the given patterns
    76.       +(pattern-list)
    77.              Matches one or more occurrences of the given patterns
    78.       @(pattern-list)
    79.              Matches exactly one of the given patterns
    80.       !(pattern-list)
    81.              Matches  anything  except  one  of the given patterns
    84. EXAMPLES
    86.     Pipelines are okay:
    87.       onlogdo /var/log/messages ‘*‘ ‘sleep 5; echo olleH | rev‘
    89.     Wildcards match filenames as usual in a command:
    90.       onlogdo /var/log/messages ‘Segfault‘ ‘rm /*.core‘
    92.     Multiple pattern and command pairs are allowed:
    93.       onlogdo /var/log/messages \
    94.             ‘ep0 at pcmcia‘ ‘/etc/rc.d/dhclient start‘ \
    95.             ‘ep0 detached‘  ‘/etc/rc.d/dhclient stop‘  \
    96.             ‘wi0 at pcmcia‘ ‘/etc/rc.d/dhclient start‘ \
    97.             ‘wi0 detached‘  ‘/etc/rc.d/dhclient stop‘
    99.     Bash’s extended pathname globbing to do the same as above:
    100.       onlogdo /var/log/messages \
    101.             ‘@(ep|wi)[0-9] at pcmcia’ ‘/etc/rc.d/dhclient start’ \
    102.             ‘@(ep|wi)[0-9] detached’  ‘/etc/rc.d/dhclient stop’
    104.     A useful example for NetBSD/hpcmips:
    105.       onlogdo /var/log/messages ‘hpcapm: resume’ ‘sleep 1; xrefresh’
    107.     Under NetBSD/hpcmips-1.5.1, the X server screen is overwritten by the
    108.     console on an APM resume. I put the last “onlogdo” example in my
    109.     system xinitrc, so xrefresh will be run automatically. (The sleep
    110.     is there to wait for the console to finish junking up the screen).
    113. SEE ALSO
    115.     tail(1), bash(1)
    117. BUGS
    119.     If this had been written in Perl it would have used “normal”
    120.     regexp syntax instead of pathname expansion. Bash‘s extensions
    121.     make the patterns as powerful as regexps, but more recondite.
    123.     There is no (documented) way for a command to refer to specifics
    124.     in the line that matched. E.g., if the pattern was “@(ep|wi)0”,
    125.     the command wouldn’t know if the line contained ep0 or wi0.
    127.     The author has spent way too much time perfecting a kludge. No
    128.     matter what you‘re using onlogdo for, there’s probably a more
    129.     “correct” way to do it. On the other hand, onlogdo is widely
    130.     applicable and easy to use, so at least you won‘t be wasting much
    131.     time while doing it the “wrong” way.
    133.     There should be a real man page.
    136. AUTHOR
    138.     Ben Wong <Benjamin.Wong@cc.gatech.edu>
    141. HISTORY
    143.     Onlogdo started life as a one line kludge to work around a bug in
    144.     the interaction between APM and the X server in NetBSD-1.5/hpcmips
    145.     in September of 2001.
    147. EOF
    148. }
    154. ### USAGE AND ARGUMENT SANITY CHECKING ###
    156. if [[ $# -lt 3 ]]; then
    157.     showmanpage
    158.     exit 1
    159. fi
    161. # Emacs’s syntax highlighting doesn‘t handle single ticks (‘) properly.
    165. # Check if -v (verbose) flag was given.
    166. if [[ “$1” == “-v” ]]; then
    167.     ifverbose=echo            # Echo commands verbosely, if -v.
    168.     shift
    169. else
    170.     ifverbose=:   # Usually just run a no-op.
    171. fi
    174. # Make sure the log file is readable.
    175. if [[ ! -r “$1” ]]; then
    176.     echo “onlogdo: \”$1\” is not readable” >&2
    177.     exit 1
    178. fi
    179. if [[ -d “$1” ]]; then
    180.     echo “onlogdo: \”$1\” is a directory” >&2
    181.     exit 1
    182. fi
    189. ### SIGNAL HANDLING AND EXIT CLEANUP ###
    191. # Run cleanup function when shell exits.
    192. trap cleanup EXIT
    195. cleanup () {
    196.     echo “onlogdo: cleaning up…” >&2
    197.     if [[ “$TAILPID” ]]; then
    198.         kill $TAILPID      # Kill the bg tail process.
    199.     fi
    200.     rm -f “$PIPE”              # Delete the named pipe.
    201.     rmdir “$PIPEDIR”
    202.     return 0
    203. }
    208. ### MAIN ROUTINE STARTS HERE ###
    210. # Don’t expand wildcards in pattern arguments as filenames.
    211. set -o noglob
    213. # Use bash’s extended pattern matching operators
    214. shopt -s extglob
    216. # Create a pipe to read the log file a line at a time;
    217. # Use mktemp for security.
    219. PIPEDIR=$(mktemp -d /tmp/onlogdo.XXXXXX)
    220. PIPE=“$PIPEDIR/$(echo $1 | sed ‘s#^/##; s#/#.#g’)”      # var.log.messages
    221. rm -f $PIPE
    222. mknod $PIPE p
    223. tail -Fn0 $1 >$PIPE &      # FSF tail: “tail –retry -fn0”
    224. TAILPID=$!
    225. exec 5< $PIPE
    227. # Copy the positional paramaters in to a variable that can be indexed.
    228. params=(“$0” “$@”)
    231. # Repeatedly read from the pipe, process each line.
    232. while :; do
    233.     while read REPLY <&5; do
    235.         $ifverbose -e “\nline: \”$REPLY\”“
    236.         for ((i=2; i<$#; i+=2)); do
    237.             pattern=${params[$i]}
    238.             command=${params[$((i+1))]}
    239.             $ifverbose “pattern: \”$pattern\”“
    240.             if [[ -z “${REPLY##*$pattern*}” ]]; then
    241.                 $ifverbose “*MATCHED*”
    242.                 $ifverbose “command: \”$command\”“
    243.                 set +o noglob   # Allow pathname matching in commands
    244.                 eval $command &
    245.                 set -o noglob   # No pathname expansion for patterns
    246.             fi
    247.         done
    248.     done
    250.     # We get here whenever the pipe first blocks (returns EOF)
    251.     sleep 1               # Don’t loop too quickly
    252. done
    255. ### MAIN ROUTINE ENDS HERE ###
    258. # Note: if we ever get here, the cleanup() function will be called
    259. # automatically since we’re trapping on signal 0.
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  • Quelque cron bien utiles
    8 years ago
    Syntaxe:
minute : de 0 à 59
heure : de 0 à 23
jour du mois de : 1 à 31
mois de : 1 à 12
jour de la semaine : de 0 à 7, 0 et 7 étant le dimanche et ainsi de suite.
commande : peut comporter plusieurs commandes.

Extra:
- Les mois et les jours peuvent aussi être donnés avec les abréviations anglaises :jan,feb,... et mon,tue,...
- On sépare les jours, les mois par des , (virgules), par exemple pour lancer une action tous les 15 et 30 du mois tapez 15,30 à la place de jour du mois.
- Le '-' signifie jusqu'à, ainsi 15-30 signifie du 15 au 30.
- Le '/' permet de spécifier une répétition, */3 indique toutes les 3 minutes.
- '*' peut être utilisée et indique tous les jours de semaine, tous les mois, toutes les heures.

Exemples:
*/3 * * * * commande   -->  toutes les X minutes.
0 0 * * * commande      --> tous les jours à minuit
30 23 */3 * * commande   --> tous les 3 jours à 23h30
0 0 * * 7 commande      --> tous les dimanche à minuit
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