mdw@git.distorted.org.uk Git - misc/blob - hush.in

   1 #! /bin/sh
   2 ###
   3 ### Run a program, but stash its output unless it fails
   4 ###
   5 ### (c) 2011 Mark Wooding
   6 ###
   7
   8 ###----- Licensing notice ---------------------------------------------------
   9 ###
  10 ### This program is free software; you can redistribute it and/or modify
  11 ### it under the terms of the GNU General Public License as published by
  12 ### the Free Software Foundation; either version 2 of the License, or
  13 ### (at your option) any later version.
  14 ###
  15 ### This program is distributed in the hope that it will be useful,
  16 ### but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ### GNU General Public License for more details.
  19 ###
  20 ### You should have received a copy of the GNU General Public License
  21 ### along with this program; if not, write to the Free Software
  22 ### Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  23
  24 set -e
  25
  26 quis=${0##*/}
  27 usage="usage: $quis [-d DIR] [-m EMAIL] [-n NLOG] TAG COMMAND [ARGS ...]"
  28 ver="@VERSION@"
  29 version () { echo "$quis, @PACKAGE@ version $ver"; }
  30
  31 ###--------------------------------------------------------------------------
  32 ### Parse the command line.
  33
  34 ## Initialize variables for storing command-line option values.
  35 logdir="@logdir@"
  36 maxlog=16
  37 unset mail
  38 unset owner
  39 unset mode
  40
  41 ## Scan the options.
  42 while getopts "hvd:m:n:p:u:" opt; do
  43   case "$opt" in
  44     h)
  45       version
  46       cat <<EOF
  47
  48 $usage
  49
  50 Run COMMAND with ARGS, logging output to DIR: if COMMAND succeeds, output
  51 nothing; if it fails, also write its output to stdout or mail it to EMAIL.
  52
  53 Options:
  54   -h                    Show this help text and exit.
  55   -v                    Show the program's version number and exit.
  56
  57   -d DIR                Write log files to DIR (default $logdir).
  58   -m EMAIL              Send email on failure to EMAIL.
  59   -n MAXLOG             Keep at most MAXLOG log files (default $maxlog).
  60   -p MODE               Set log permissions to MODE (default umask).
  61   -u [OWNER][:GROUP]    Set log file OWNER and GROUP (default system).
  62 EOF
  63       exit
  64       ;;
  65     v)
  66       version
  67       exit
  68       ;;
  69
  70     d) logdir=$OPTARG ;;
  71     m) mail=$OPTARG ;;
  72     n) maxlog=$OPTARG ;;
  73     p) mode=$OPTARG ;;
  74     u) owner=$OPTARG ;;
  75     *) echo >&2 "$usage"; exit 1 ;;
  76   esac
  77 done
  78 shift $(( $OPTIND - 1 ))
  79
  80 ## Check the arguments.
  81 case $# in 0 | 1) echo >&2 "$usage"; exit 1 ;; esac
  82 tag=$1 cmd=$2; shift 2
  83
  84 ###--------------------------------------------------------------------------
  85 ### Check out the environment.
  86
  87 ## Force a command to line-buffer its output.  How does one do this on BSD,
  88 ## for example?
  89 if stdbuf --version >/dev/null 2>&1; then
  90   lbuf="stdbuf -oL --"
  91 else
  92   lbuf=""
  93 fi
  94
  95 ###--------------------------------------------------------------------------
  96 ### Set up the log file.
  97
  98 ## Find a name for the log file.  In unusual circumstances, we may have
  99 ## deleted old logs from today, so just checking for an unused sequence
 100 ## number is insufficient.  Instead, check all of the logfiles for today, and
 101 ## use a sequence number that's larger than any of them.
 102 date=$(date +%Y-%m-%d) seq=1
 103 for i in "$logdir/$tag.$date#"*; do
 104   tail=${i##*#}
 105   case "$tail" in [!1-9]* | *[!0-9]*) continue ;; esac
 106   if [ -f "$i" -a $tail -ge $seq ]; then seq=$(( $tail + 1 )); fi
 107 done
 108 log="$logdir/$tag.$date#$seq"
 109
 110 ## Create the file.  Make sure we create it with restrictive permissions
 111 ## and then slacken them off if necessary.  This means that we don't (for
 112 ## example) end up giving the wrong group write permission to the file for a
 113 ## little bit.
 114 umask=$(umask)
 115 case ${mode+t} in t) ;; *) mode=$(printf %o $(( 0666 & ~$umask ))) ;; esac
 116 umask 077; exec 3>"$log"; umask $umask
 117 case ${owner+t} in t) chown "$owner" "$log" ;; esac
 118 chmod $mode "$log"
 119
 120 ###--------------------------------------------------------------------------
 121 ### Run the program.
 122
 123 ## Write a log header.
 124 cat >&3 <<EOF
 125         Started $cmd at $(date +"%Y-%m-%d %H:%M:%S %z")
 126         Lines beginning \`|' are stdout; lines beginning \`*' are stderr
 127
 128 EOF
 129
 130 ## Run the program, interleaving stdout and stderr in a vaguely useful way.
 131 ## This involves what I can only describe as a `shell game' (sorry) with file
 132 ## descriptors.
 133 ##
 134 ## In the middle, we have the actual command, hacked so as to line-buffer
 135 ## stdout (so that we can better interleave stderr).  We capture its stdout
 136 ## and stderr into pipelines, one at a time, in which we pluck out lines one
 137 ## by one and prefix them with distinctive characters, and then write them to
 138 ## another pipe (fd 4) which is written via cat(1) to the log file.  (This is
 139 ## not a `useless use of cat': I rely on the write atomicity guarantee of
 140 ## pipes in order to prevent intermingling of the stdout and stderr lines --
 141 ## of course, if they're too long to fit in the pipe buffer then we'll just
 142 ## lose.)
 143 ##
 144 ## Finally, there's a problem because we only get the exit status of the last
 145 ## stage of a pipeline, where we actually wanted the status of the first.  So
 146 ## we write that to another pipe (fd 5) and pick it out using command
 147 ## substitution.
 148 copy () { while IFS= read -r line; do printf "%s %s\n" "$1" "$line"; done; }
 149 rc=$(
 150   { { { { set +e; $lbuf "$cmd" "$@" 3>&- 4>&- 5>&-; echo $? >&5; } |
 151         copy "|" >&4; } 2>&1 |
 152       copy "*" >&4; } 4>&1 |
 153     cat -u >&3; } 5>&1 </dev/null
 154 )
 155
 156 ## Write the log trailer.
 157 cat >&3 <<EOF
 158
 159         Ended $cmd at $(date +"%Y-%m-%d %H:%M:%S %z") with status $rc
 160 EOF
 161 exec 3>&-
 162
 163 ###--------------------------------------------------------------------------
 164 ### Delete old log files if there are too many.
 165
 166 ## Find out the tails of the logfile names.  We assume that we're responsible
 167 ## for all of these, and therefore that they're nicely formed.
 168 logs="" nlog=0
 169 for i in "$logdir/$tag".*; do
 170   if [ ! -f "$i" ]; then continue; fi
 171   nlog=$(( $nlog + 1 ))
 172   logs="$logs ${i#$logdir/$tag.}"
 173 done
 174
 175 ## If there are too many, go through and delete some early ones.
 176 if [ $nlog -gt $maxlog ]; then
 177   n=$(( $nlog - $maxlog ))
 178   for i in $logs; do echo $i; done | sort -t# -k1,1 -k2n | while read i; do
 179     rm -f "$logdir/$tag.$i"
 180     n=$(( $n - 1 ))
 181     if [ $n -eq 0 ]; then break; fi
 182   done
 183 fi
 184
 185 ###--------------------------------------------------------------------------
 186 ### Do something useful with the result.
 187
 188 case $rc,${mail+t} in
 189   0,*)
 190     ## Everything worked.  Leave the results in the log file in case someone
 191     ## cares.
 192     ;;
 193   *,t)
 194     ## Failed, and we have an email address.  Send mail and appear to
 195     ## succeed: we've done our job and reported the situation.  The idea is
 196     ## to prevent something else (e.g., cron) from producing another report
 197     ## for the same problem, but without the useful content.
 198     mail -s "$tag: $cmd failed (status = $rc)" "$mail" <"$log"
 199     rc=0
 200     ;;
 201   *)
 202     ## Failed, and no email address.  Write the accumulated stuff.
 203     cat "$log"
 204     ;;
 205 esac
 206
 207 ## Exit with an appropriate status.
 208 exit $rc
 209
 210 ###----- That's all, folks --------------------------------------------------