X-Git-Url: https://iankelling.org/git/?p=log-quiet;a=blobdiff_plain;f=log-once;h=5980b811423413ed01a33222112313b42b73ae94;hp=4a2b3480e5c8dbc20771feb9df20bef5646ce008;hb=HEAD;hpb=9d651c1e48698ebd746a182d059291e76989601a

diff --git a/log-once b/log-once
index 4a2b348..8cfe388 100755
--- a/log-once
+++ b/log-once
@@ -1,33 +1,82 @@
 #!/bin/bash
+# I, Ian Kelling, follow the GNU license recommendations at
+# https://www.gnu.org/licenses/license-recommendations.en.html. They
+# recommend that small programs, < 300 lines, be licensed under the
+# Apache License 2.0. This file contains or is part of one or more small
+# programs. If a small program grows beyond 300 lines, I plan to switch
+# its license to GPL.
+
+# Copyright 2024 Ian Kelling
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
 # Copyright (C) 2019 Ian Kelling
-# SPDX-License-Identifier: AGPL-3.0-or-later
+# Log errors once or so instead of many times.
+
+    # This program is free software: you can redistribute it and/or modify
+    # it under the terms of the GNU General Public License as published by
+    # the Free Software Foundation, either version 3 of the License, or
+    # (at your option) any later version.
+
+    # This program is distributed in the hope that it will be useful,
+    # but WITHOUT ANY WARRANTY; without even the implied warranty of
+    # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    # GNU General Public License for more details.
+
+    # You should have received a copy of the GNU General Public License
+    # along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# SPDX-License-Identifier: GPL-3.0-or-later
 
 append() {
   cat >> "$1"
 }
 log-once() {
-  local cbase c log x i out file o tmp
+  local cbase c log line i out file o tmp mvout mverr verbose
   cbase=/var/local/cron-errors
   [[ $EUID == 0 ]] || cbase=$HOME/cron-errors
-  local help="Usage: log-once [OPTION]... LOG_NAME [LOG_MESSAGE...]
+  local help="Usage: some-command-that-outputs-on-error |& log-once [OPTION]... LOG_NAME
 
-For cronjobs, email log on repeated failure and success after failure.
-
-Meant for use in cronjobs where LOG_MESSAGE or STDIN represents an error,
+Main use case: in cronjobs where STDIN represents an error,
 but we only want to output that to STDOUT if we've seen this type of
 error ERRORS(default 3) number of times in a row, then we don't
-want to output anything again until we've seen a success (an empty LOG_MESSAGE).
+want to output anything again until we've seen a success: no standard input.
+
+Logs STDIN to /var/local/cron-errors/LOG_NAME\$error_count or
+$HOME/cron-errors if not root, and keeps state in the same directory.
 
-Logs LOG_MESSAGE or STDIN to /var/local/cron-errors/LOG_NAME\$error_count
-or $HOME/cron-errors if not root, and keeps
-state in the same directory.
+-ERRORS:  ERRORS is the number of errors to accumulate before outputing the error
+-v:       Output the errors along the way to ERRORS
 
--ERRORS:  ERRORS is the number of errors to accumulate before outputing the error"
+
+You can emulate how cronjobs work by doing this for example:
+
+    cmdname |& log-once | ifne mail -s 'cmdname failed' root@localhost
+
+I could imagine a similar command that considers its non-option args to
+be an error, but I haven't written it yet.
+"
   errors=3
+  mverr=0
+  verbose=false
+
   while true; do
     if [[ $1 == --help ]]; then
       echo "$help"
       return
+    elif [[ $1 == -v ]]; then
+      verbose=true
+      shift
     elif [[ $1 == -[0-9]* ]]; then
       errors=${1#-}
       shift
@@ -42,17 +91,15 @@ state in the same directory.
   # todo, make option & make them overridable based on command line or env variable
   [[ -d $cbase ]] || mkdir -p $cbase
   c=$cbase/$log_name
-  # http://stackoverflow.com/questions/2456750/detect-presence-of-stdin-contents-in-shell-script
   log=false
-  if [[ $2 ]]; then
-    log=true
-    # read stdin for anything which is not just a newline
-  elif [[ ! -t 0 ]]; then
-    while read -r x; do
-      output+=( "$x" )
-      [[ $x ]] && log=true
-    done
-  fi
+  while read -r line; do
+    output+=( "$line" )
+    # If we find something that is not just a newline:
+    if [[ $line ]]; then
+      log=true
+      break
+    fi
+  done
   glob="$c[0-9]*"
   # file is error file indicating previous error
   tmp=($glob); file="${tmp[0]}"
@@ -65,9 +112,19 @@ state in the same directory.
       i="${file#$c}"
       if (( i < errors )); then
         new_file=$c$((i+1))
-        mv $file $new_file
+        mvout=$(mv $file $new_file 2>&1) || mverr=$?
+        if (( mverr )); then
+          if [[ $mvout == *": No such file or directory" ]]; then
+            # We've very likely hit a race condition, where another
+            # log-once did the mv before us.
+            return 0
+          else
+            echo "log-once: error on mv $file $new_file"
+            return $mverr
+          fi
+        fi
         file=$new_file
-        if [[ $file == $c$errors ]]; then
+        if [[ $file == $c$errors ]] || $verbose; then
           out="tee -a"
         fi
       fi
@@ -77,7 +134,7 @@ state in the same directory.
         out="tee -a"
       fi
     fi
-    $out $file <<<"log-once: $(date "+%A, %B %d, %r")"
+    $out $file <<<"log-once: $(date -R)"
     if [[ $2 ]]; then
       $out $file <<<"$*"
     else
@@ -91,7 +148,7 @@ state in the same directory.
   if [[ $file ]]; then
     rm -f $file
     if [[ $file == $c$errors ]]; then
-      echo "log-once success after failure for $c"
+      echo "log-once: $(date -R): success after failure for $c"
     fi
   fi
   return 0