iankelling.org Git - log-quiet/blob - log-once

   1 #!/bin/bash
   2 # Copyright (C) 2019 Ian Kelling
   3 # SPDX-License-Identifier: AGPL-3.0-or-later
   4
   5 append() {
   6   cat >> "$1"
   7 }
   8 log-once() {
   9   local cbase c log line i out file o tmp
  10   cbase=/var/local/cron-errors
  11   [[ $EUID == 0 ]] || cbase=$HOME/cron-errors
  12   local help="Usage: some-command-that-outputs-on-error |& log-once [OPTION]... LOG_NAME
  13
  14 Main use case: in cronjobs where STDIN represents an error,
  15 but we only want to output that to STDOUT if we've seen this type of
  16 error ERRORS(default 3) number of times in a row, then we don't
  17 want to output anything again until we've seen a success: no standard input.
  18
  19 Logs STDIN to /var/local/cron-errors/LOG_NAME\$error_count or
  20 $HOME/cron-errors if not root, and keeps state in the same directory.
  21
  22 -ERRORS:  ERRORS is the number of errors to accumulate before outputing the error
  23
  24
  25 You can emulate how cronjobs work by doing this for example:
  26
  27     cmdname |& log-once | ifne mail -s 'cmdname failed' root@localhost
  28
  29 I could imagine a similar command that considers its non-option args to
  30 be an error, but I haven't written it yet.
  31 "
  32   errors=3
  33   while true; do
  34     if [[ $1 == --help ]]; then
  35       echo "$help"
  36       return
  37     elif [[ $1 == -[0-9]* ]]; then
  38       errors=${1#-}
  39       shift
  40     elif [[ $1 == -- ]]; then
  41       shift
  42       break
  43     else
  44       break
  45     fi
  46   done
  47   log_name=$1
  48   # todo, make option & make them overridable based on command line or env variable
  49   [[ -d $cbase ]] || mkdir -p $cbase
  50   c=$cbase/$log_name
  51   log=false
  52   while read -r line; do
  53     output+=( "$line" )
  54     # If we find something that is not just a newline:
  55     if [[ $line ]]; then
  56       log=true
  57       break
  58     fi
  59   done
  60   glob="$c[0-9]*"
  61   # file is error file indicating previous error
  62   tmp=($glob); file="${tmp[0]}"
  63   if [[ $file == "$glob" ]]; then
  64     file=
  65   fi
  66   if $log; then
  67     out=append
  68     if [[ $file ]]; then
  69       i="${file#$c}"
  70       if (( i < errors )); then
  71         new_file=$c$((i+1))
  72         mv $file $new_file
  73         file=$new_file
  74         if [[ $file == $c$errors ]]; then
  75           out="tee -a"
  76         fi
  77       fi
  78     else
  79       file=${c}1
  80       if (( errors == 1 )); then
  81         out="tee -a"
  82       fi
  83     fi
  84     $out $file <<<"log-once: $(date -R)"
  85     if [[ $2 ]]; then
  86       $out $file <<<"$*"
  87     else
  88       for o in "${output[@]}"; do
  89         $out $file <<<"$o"
  90       done
  91       $out $file
  92     fi
  93     return 0
  94   fi
  95   if [[ $file ]]; then
  96     rm -f $file
  97     if [[ $file == $c$errors ]]; then
  98       echo "log-once: $(date -R): success after failure for $c"
  99     fi
 100   fi
 101   return 0
 102 }
 103 log-once "$@"