I cant seem to make this work.
This is the script.
tail -fn0 nohup.out | while read line; do
if [[ "${line}" =~ ".*ERIKA.*" ]]; then
echo "match found"
break
fi
done
echo "Search done"
The code echo "Search done" does not run even after a match has been found.
I just want the rest of the code to be ran when a match has been found.
I have not made it possible yet.
Sorry, I am new with log monitoring.
Is there any workaround with this?
I am gonna run the script via Jenkins so, the code should be free flowing
and should not require any user interaction.
Please help, thanks.
You've got a couple of issues here:
tail is going to keep running until it fails to write to its output pipeline, and thus your pipeline won't complete until tail exits. It won't do that until after your script exits, AND another line (or possibly 4K if buffering, see below) is written to the log file, causing it to attempt to write to its output pipe. (re buffering: Most programs are switched to 4K buffering when writing through pipes. Unless tail explicitly sets its buffering, this would affect the above behaviour).
your regex: "${line}" =~ ".*ERIKA.*" does not match for me. However, "${line}" =~ "ERIKA" does match.
You can use tail's --pid option as a solution to the first issue. Here's an example, reworking your script to use that option:
while read line; do
if [[ "${line}" =~ "ERIKA" ]]; then
echo "match found"
break
fi
done < <(tail --pid=$$ -f /tmp/out)
echo "Search done"
Glenn Jackman's pkill solution is another approach to terminating the tail.
Perhaps consider doing this in something other than bash: perl has a nice File::Tail module that implements the tail behaviour.
There are many more questions related to this problem, you may find something you prefer in their answers:
Ending tail -f started in a shell script
Do a tail -F until matching a pattern
https://superuser.com/questions/275827/how-to-read-one-line-from-tail-f-through-a-pipeline-and-then-terminate
https://unix.stackexchange.com/questions/45941/tail-f-until-text-is-seen
https://unix.stackexchange.com/questions/12075/best-way-to-follow-a-log-and-execute-a-command-when-some-text-appears-in-the-log?rq=1
Here's one way, doesn't feel very elegant though.
tail -fn0 nohup.out |
while IFS= read -r line; do
if [[ $line == *ERIKA* ]]; then
echo "match found"
pkill -P $$ tail
fi
done
echo "Search done"
You can use awk to exit:
tail -fn0 nohup.out | awk '/ERIKA/{print "match found ", $0; exit}'
Related
Is there a way to monitor a log file using shell script like
tail -f /var/log/errorlog.txt then if something like down keyword appears, then generate SNMPTRAP to snmp manager and continues the monitoring
I have a SNMP script available to generate SNMPTrap and it looks like
snmptrap -v v2c -c community host "Error message"
Lets the say the script name is snmp.sh
My question is how to perform the below operation
tail the logs
if keyword[down] matches then use snmp.sh script to send alert
else leave
As per the suggestion i tried this
tail -F /data/log/test.log |
egrep -io 'got signal 15 | now exiting' |
while read -r line ;
do
case "$line" in
"got signal 15")
echo "hi"
;;
"now exiting")
echo "hi2"
;;
*)
esac
done
but the problem is tail is not working here with case statement, whenever the new log details added its not going to the case statement and echos the output
I could get the output if i use cat/less/more
Could you someone please tell what mistake i have done here ?
Thanks in advance
It sounds like the pattern you want is this:
tail -f /var/log/errorlog.txt | grep -e down -e unmounted | while read -r line
do
case "$line" in
down)
./snmp.sh …
;;
unmounted)
./snmp.sh …
;;
*)
echo "Unhandled keyword ${line}" >&2
exit 1
esac
done
try
tail -f /var/log/errorlog.txt | grep "down" | while read line; do snmp.sh; done
Please explain to me why the very last echo statement is blank? I expect that XCODE is incremented in the while loop to a value of 1:
#!/bin/bash
OUTPUT="name1 ip ip status" # normally output of another command with multi line output
if [ -z "$OUTPUT" ]
then
echo "Status WARN: No messages from SMcli"
exit $STATE_WARNING
else
echo "$OUTPUT"|while read NAME IP1 IP2 STATUS
do
if [ "$STATUS" != "Optimal" ]
then
echo "CRIT: $NAME - $STATUS"
echo $((++XCODE))
else
echo "OK: $NAME - $STATUS"
fi
done
fi
echo $XCODE
I've tried using the following statement instead of the ++XCODE method
XCODE=`expr $XCODE + 1`
and it too won't print outside of the while statement. I think I'm missing something about variable scope here, but the ol' man page isn't showing it to me.
Because you're piping into the while loop, a sub-shell is created to run the while loop.
Now this child process has its own copy of the environment and can't pass any
variables back to its parent (as in any unix process).
Therefore you'll need to restructure so that you're not piping into the loop.
Alternatively you could run in a function, for example, and echo the value you
want returned from the sub-process.
http://tldp.org/LDP/abs/html/subshells.html#SUBSHELL
The problem is that processes put together with a pipe are executed in subshells (and therefore have their own environment). Whatever happens within the while does not affect anything outside of the pipe.
Your specific example can be solved by rewriting the pipe to
while ... do ... done <<< "$OUTPUT"
or perhaps
while ... do ... done < <(echo "$OUTPUT")
This should work as well (because echo and while are in same subshell):
#!/bin/bash
cat /tmp/randomFile | (while read line
do
LINE="$LINE $line"
done && echo $LINE )
One more option:
#!/bin/bash
cat /some/file | while read line
do
var="abc"
echo $var | xsel -i -p # redirect stdin to the X primary selection
done
var=$(xsel -o -p) # redirect back to stdout
echo $var
EDIT:
Here, xsel is a requirement (install it).
Alternatively, you can use xclip:
xclip -i -selection clipboard
instead of
xsel -i -p
I got around this when I was making my own little du:
ls -l | sed '/total/d ; s/ */\t/g' | cut -f 5 |
( SUM=0; while read SIZE; do SUM=$(($SUM+$SIZE)); done; echo "$(($SUM/1024/1024/1024))GB" )
The point is that I make a subshell with ( ) containing my SUM variable and the while, but I pipe into the whole ( ) instead of into the while itself, which avoids the gotcha.
#!/bin/bash
OUTPUT="name1 ip ip status"
+export XCODE=0;
if [ -z "$OUTPUT" ]
----
echo "CRIT: $NAME - $STATUS"
- echo $((++XCODE))
+ export XCODE=$(( $XCODE + 1 ))
else
echo $XCODE
see if those changes help
Another option is to output the results into a file from the subshell and then read it in the parent shell. something like
#!/bin/bash
EXPORTFILE=/tmp/exportfile${RANDOM}
cat /tmp/randomFile | while read line
do
LINE="$LINE $line"
echo $LINE > $EXPORTFILE
done
LINE=$(cat $EXPORTFILE)
I have been writing a bash script to call in my .bashrc file to print the results of whatis for a random command in my /usr/bin folder and wanted to exclude commands that returned "nothing appropriate" in the result and even if I use grep, wc, expr, ==, nothing seems to work. I have pretty much used every example here, and here with no progress. This is what I have so far but failes to do what I want when it finds somthing that contains "nothing appropriate." If anyone could figure out how to get it to work or what a good solution would be in this situation I would be greatfull.
#! /bin/bash
echo "Did you know that:";
while :
do
RESULT=$(whatis $(ls /usr/bin | shuf -n 1))
if [[ $RESULT != *"nothing appropriate"* ]]
then
echo $RESULT
break
fi
done
whatis prints the nothing appropriate message on the standard error stream. This stream is not caught by the $( ). This is the reason of your issue.
This is a way to fix it:
#! /bin/bash
echo "Did you know that:";
while :
do
RESULT=$(whatis $(ls /usr/bin | shuf -n 1) 2>&1 | cat - )
if [[ $RESULT != *"nothing appropriate"* ]]
then
echo $RESULT
break
fi
done
The 2>&1 | cat - addition does the trick
I work with some log system which creates a log file every hour, like follows:
SoftwareLog.2010-08-01-08
SoftwareLog.2010-08-01-09
SoftwareLog.2010-08-01-10
I'm trying to tail to follow the latest log file giving a pattern (e.g. SoftwareLog*) and I realize there's:
tail -F (tail --follow=name --retry)
but that only follow one specific name - and these have different names by date and hour. I tried something like:
tail --follow=name --retry SoftwareLog*(.om[1])
but the wildcard statement is resoved before it gets passed to tail and doesn't re-execute everytime tail retries.
Any suggestions?
I believe the simplest solution is as follows:
tail -f `ls -tr | tail -n 1`
Now, if your directory contains other log files like "SystemLog" and you only want the latest "SoftwareLog" file, then you would simply include a grep as follows:
tail -f `ls -tr | grep SoftwareLog | tail -n 1`
[Edit: after a quick googling for a tool]
You might want to try out multitail - http://www.vanheusden.com/multitail/
If you want to stick with Dennis Williamson's answer (and I've +1'ed him accordingly) here are the blanks filled in for you.
In your shell, run the following script (or it's zsh equivalent, I whipped this up in bash before I saw the zsh tag):
#!/bin/bash
TARGET_DIR="some/logfiles/"
SYMLINK_FILE="SoftwareLog.latest"
SYMLINK_PATH="$TARGET_DIR/$SYMLINK_FILE"
function getLastModifiedFile {
echo $(ls -t "$TARGET_DIR" | grep -v "$SYMLINK_FILE" | head -1)
}
function getCurrentlySymlinkedFile {
if [[ -h $SYMLINK_PATH ]]
then
echo $(ls -l $SYMLINK_PATH | awk '{print $NF}')
else
echo ""
fi
}
symlinkedFile=$(getCurrentlySymlinkedFile)
while true
do
sleep 10
lastModified=$(getLastModifiedFile)
if [[ $symlinkedFile != $lastModified ]]
then
ln -nsf $lastModified $SYMLINK_PATH
symlinkedFile=$lastModified
fi
done
Background that process using the normal method (again, I don't know zsh, so it might be different)...
./updateSymlink.sh 2>&1 > /dev/null
Then tail -F $SYMLINK_PATH so that the tail hands the changing of the symbolic link or a rotation of the file.
This is slightly convoluted, but I don't know of another way to do this with tail. If anyone else knows of a utility that handles this, then let them step forward because I'd love to see it myself too - applications like Jetty by default do logs this way and I always script up a symlinking script run on a cron to compensate for it.
[Edit: Removed an erroneous 'j' from the end of one of the lines. You also had a bad variable name "lastModifiedFile" didn't exist, the proper name that you set is "lastModified"]
I haven't tested this, but an approach that may work would be to run a background process that creates and updates a symlink to the latest log file and then you would tail -f (or tail -F) the symlink.
#!/bin/bash
PATTERN="$1"
# Try to make sure sub-shells exit when we do.
trap "kill -9 -- -$BASHPID" SIGINT SIGTERM EXIT
PID=0
OLD_FILES=""
while true; do
FILES="$(echo $PATTERN)"
if test "$FILES" != "$OLD_FILES"; then
if test "$PID" != "0"; then
kill $PID
PID=0
fi
if test "$FILES" != "$PATTERN" || test -f "$PATTERN"; then
tail --pid=$$ -n 0 -F $PATTERN &
PID=$!
fi
fi
OLD_FILES="$FILES"
sleep 1
done
Then run it as: tail.sh 'SoftwareLog*'
The script will lose some log lines if the logs are written to between checks. But at least it's a single script, with no symlinks required.
We have daily rotating log files as: /var/log/grails/customer-2020-01-03.log. To tail the latest one, the following command worked fine for me:
tail -f /var/log/grails/customer-`date +'%Y-%m-%d'`.log
(NOTE: no space after the + sign in the expression)
So, for you, the following should work (if you are in the same directory of the logs):
tail -f SoftwareLog.`date +'%Y-%m-%d-%H'`
I believe the easiest way is to use tail with ls and head, try something like this
tail -f `ls -t SoftwareLog* | head -1`
I have a shell script that saves the output of a command that is executed to a CSV file. It reads the command it has to execute from a shell script which is in this format:
ffmpeg -i /home/test/videos/avi/418kb.avi /home/test/videos/done/418kb.flv
ffmpeg -i /home/test/videos/avi/1253kb.avi /home/test/videos/done/1253kb.flv
ffmpeg -i /home/test/videos/avi/2093kb.avi /home/test/videos/done/2093kb.flv
You can see each line is an ffmpeg command. However, the script just executes the first line. Just a minute ago it was doing nearly all of the commands. It was missing half for some reason. I edited the text file that contained the commands and now it will only do the first line. Here is my bash script:
#!/bin/bash
# Shell script utility to read a file line line.
# Once line is read it will run processLine() function
#Function processLine
processLine(){
line="$#"
START=$(date +%s.%N)
eval $line > /dev/null 2>&1
END=$(date +%s.%N)
DIFF=$(echo "$END - $START" | bc)
echo "$line, $START, $END, $DIFF" >> file.csv 2>&1
echo "It took $DIFF seconds"
echo $line
}
# Store file name
FILE=""
# get file name as command line argument
# Else read it from standard input device
if [ "$1" == "" ]; then
FILE="/dev/stdin"
else
FILE="$1"
# make sure file exist and readable
if [ ! -f $FILE ]; then
echo "$FILE : does not exists"
exit 1
elif [ ! -r $FILE ]; then
echo "$FILE: can not read"
exit 2
fi
fi
# read $FILE using the file descriptors
# Set loop separator to end of line
BAKIFS=$IFS
IFS=$(echo -en "\n\b")
exec 3<&0
exec 0<$FILE
while read line
do
# use $line variable to process line in processLine() function
processLine $line
done
exec 0<&3
# restore $IFS which was used to determine what the field separators are
BAKIFS=$ORIGIFS
exit 0
Thank you for any help.
UPDATE 2
Its the ffmpeg commands rather than the shell script that isn't working. But I should of been using just "\b" as Paul pointed out. I am also making use of Johannes's shorter script.
I think that should do the same and seems to be correct:
#!/bin/bash
CSVFILE=/tmp/file.csv
cat "$#" | while read line; do
echo "Executing '$line'"
START=$(date +%s)
eval $line &> /dev/null
END=$(date +%s)
let DIFF=$END-$START
echo "$line, $START, $END, $DIFF" >> "$CSVFILE"
echo "It took ${DIFF}s"
done
no?
ffmpeg reads STDIN and exhausts it. The solution is to call ffmpeg with:
ffmpeg </dev/null ...
See the detailed explanation here: http://mywiki.wooledge.org/BashFAQ/089
Update:
Since ffmpeg version 1.0, there is also the -nostdin option, so this can be used instead:
ffmpeg -nostdin ...
I just had the same problem.
I believe ffmpeg is responsible for this behaviour.
My solution for this problem:
1) Call ffmpeg with an "&" at the end of your ffmpeg command line
2) Since now the skript will not wait till completion of the ffmpeg process,
we have to prevent our script from starting several ffmpeg processes.
We achieve this goal by delaying the loop pass while there is at least
one running ffmpeg process.
#!/bin/bash
cat FileList.txt |
while read VideoFile; do
<place your ffmpeg command line here> &
FFMPEGStillRunning="true"
while [ "$FFMPEGStillRunning" = "true" ]; do
Process=$(ps -C ffmpeg | grep -o -e "ffmpeg" )
if [ -n "$Process" ]; then
FFMPEGStillRunning="true"
else
FFMPEGStillRunning="false"
fi
sleep 2s
done
done
I would add echos before and after the eval to see what it's about to eval (in case it's treating the whole file as one big long line) and after (in case one of the ffmpeg commands is taking forever).
Unless you are planning to read something from standard input after the loop, you don't need to preserve and restore the original standard input (though it is good to see you know how).
Similarly, I don't see a reason for dinking with IFS at all. There is certainly no need to restore the value of IFS before exit - this is a real shell you are using, not a DOS BAT file.
When you do:
read var1 var2 var3
the shell assigns the first field to $var1, the second to $var2, and the rest of the line to $var3. In the case where there's just one variable - your script, for example - the whole line goes into the variable, just as you want it to.
Inside the process line function, you probably don't want to throw away error output from the executed command. You probably do want to think about checking the exit status of the command. The echo with error redirection is ... unusual, and overkill. If you're sufficiently sure that the commands can't fail, then go ahead with ignoring the error. Is the command 'chatty'; if so, throw away the chat by all means. If not, maybe you don't need to throw away standard output, either.
The script as a whole should probably diagnose when it is given multiple files to process since it ignores the extraneous ones.
You could simplify your file handling by using just:
cat "$#" |
while read line
do
processline "$line"
done
The cat command automatically reports errors (and continues after them) and processes all the input files, or reads standard input if there are no arguments left. The use of double quotes around the variable means that it is passed as a single unit (and therefore unparsed into separate words).
The use of date and bc is interesting - I'd not seen that before.
All in all, I'd be looking at something like:
#!/bin/bash
# Time execution of commands read from a file, line by line.
# Log commands and times to CSV logfile "file.csv"
processLine(){
START=$(date +%s.%N)
eval "$#" > /dev/null
STATUS=$?
END=$(date +%s.%N)
DIFF=$(echo "$END - $START" | bc)
echo "$line, $START, $END, $DIFF, $STATUS" >> file.csv
echo "${DIFF}s: $STATUS: $line"
}
cat "$#" |
while read line
do
processLine "$line"
done