I have a bash script that processes some data using inotify-tools to know when certain events took place on the filesystem. It works fine if run in the bash console, but when I try to run it as a daemon it fails. I think the reason is the fact that all the output from the inotifywait command call goes to a file, thus, the part after | while doesn't get called anymore. How can I fix that? Here is my script.
#!/bin/bash
inotifywait -d -r \
-o /dev/null \
-e close_write \
--exclude "^[\.+]|cgi-bin|recycle_bin" \
--format "%w:%&e:%f" \
$1|
while IFS=':' read directory event file
do
#doing my thing
done
So, -d tells inotifywait to run as daemon, -r to do it recursively and -o is the file in which to save the output. In my case the file is /dev/null because I don't really need the output except for processing the part after the command (| while...)
You don't want to run inotify-wait as a daemon in this case, because you want to continue process output from the command. You want to replace the -d command line option with -m, which tells inotifywait to keep monitoring the files and continue printing to stdout:
-m, --monitor
Instead of exiting after receiving a single event, execute
indefinitely. The default behaviour is to exit after the
first event occurs.
If you want things running in the background, you'll need to background the entire script.
Here's a solution using nohup: (Note in my testing, if I specified the -o the while loop didn't seem to be evaluated)
nohup inotifywait -m -r \
-e close_write \
--exclude "^[\.+]|cgi-bin|recycle_bin" \
--format "%w:%&e:%f" \
$1 |
while IFS=':' read directory event file
do
#doing my thing
done >> /some/path/to/log 2>&1 &
Related
I'm a bash noob, and I am trying to set up a sort of "hot reload" functionality for a project I'm working on using inotifywait. Ubuntu 20.04 if that matters.
Here is what I hoped would have worked:
inotifywait -m -r ../.. -e modify,create,delete |
while read line; do
custom_command
done
I'm having two problems:
Issue #1 is that custom_command takes some time to work, and so if I make more changes to the directory in the meantime, custom command appears to "queue up" custom_command, where really I just want it to keep the most recent one and drop the others.
Issue #2 is that I'm getting some sort of "double output." So for example if I bash auto-exec.sh and auto-exec.sh looks like this:
inotifywait -m -r . -q -e modify,create,delete
Then each time a change registers, I get this as output (not a mistake that it's doubled -- I get two identical lines each time there is a modification):
./ MODIFY auto-exec-testfile.txt
./ MODIFY auto-exec-testfile.txt
I should note I've tried making changes both with Visual Code Studio and gedit, with the same results.
If I modify the bash file like so:
inotifywait -m -r . -q -e modify,create,delete |
while read line; do
echo "$line"
echo "..."
done
I get the following output each time there is a change:
./ MODIFY auto-exec-testfile.txt
...
./ MODIFY auto-exec-testfile.txt
...
If I modify bash_test.sh to the following:
inotifywait -m -r . -q -e modify,create,delete |
while read line; do
echo "help me..."
done
Then I get the following each time a change is made:
help me...
help me...
What happened to the the ./ MODIFY ... line?? Presumably there's something I don't understand about bash, stdout or similar /related concepts here?
And finally, if I change the .sh file to the following:
inotifywait -m -r . -q -q -e modify,create,delete |
while read _; do
echo "help me..."
done
Then I get no output at all. This one I think I understand, because the -q -q means that inotifywait is in "super silent" mode, so there is no log and therefore nothing to trigger the while.
What I'd love to do is just trigger the code once when something changes, and drop all but the most recent execution. I'm not sure doing this using a while is entirely necessary, but I tried inotifywait -m -r . -q -q -e modify,create,delete | echo "help me..", and the script printed "help me..." once at startup, then exited on modification.
Assistance very much appreciated.
EDIT - 20201-Mar-23
I removed -m and create from the inotifywait line, and it appears to work as expected, except that it doesn't stay "up" in monitor mode. So this at least only gives me one entry from inotifywait:
notifywait -r .. -q -e modify,delete |
while read line1; do
echo ${line1}
done
Related:
inotifywait - pause monitoring while executing command
https://unix.stackexchange.com/questions/140679/using-inotify-to-monitor-a-directory-but-not-working-100
inotifywait not performing the while loop in bash script
while inotifywait -e close_write,delete .; do
pkill custom_command
custom_command&
done
I have the following shell script running a inotifywait command. I want to print the output echo to the console upon every modify event.
The script:
#!/bin/sh
while inotifywait -e modify -r -m ./ --exclude '\.sh$'; do
echo test
done
When I change one file in the specified directory, i get the standard output from inotifywait:
Setting up watches. Beware: since -r was given, this may take a while!
Watches established.
./postgres/ MODIFY postgres_test.go
./postgres/ MODIFY postgres_test.go
I have two questions:
Why is the modified event registered twice? I only updated the file once.
Why is "test" not being printed to the console in which I'm running the script?
I had a similar issue. I resolved the second part by restructuring my while:
inotifywait -e modify -r -m ./ --exclude '\.sh$' |
while read E; do
echo "----------------hello $E"
done
I want to put a file watcher on a directory in my Docker container. I'm using entrypoint.sh script to setup the script that places a file watcher. The setup is like so:
#!/bin/sh
# Trigger the script with the file watcher in the background
./bin/watcher.sh &
And the watcher.sh script contains the inotifywait command:
#!/bin/sh
inotifywait \
--event create --event delete \
--event modify --event move \
--format "%e %w%f" \
--monitor --outfile '/var/log/inotifywait.log' \
--syslog --quiet --recursive \
/etc/haproxy |
while read CHANGED;
do
echo "$CHANGED"
haproxy -W -db -f /etc/haproxy/haproxy.cfg -p /var/run/haproxy.pid -sf $(cat /var/run/haproxy.pid) &
done
However, although the watcher is listed when i check with top, and it reports changes in the defined log file, the loop never triggers. I've tried debugging the loop with simple:
touch /var/log/special.log
echo "${CHANGED}" >> /var/log/special.log
But file never gets created, and nothing gets echoed in it. What is the right way to use inotifywait with loop in bash script?
You are explicitly sending output to a file rather than stdout using the --outfile option. Nothing is ever written to stdout, so the read statement in your while loop never reads any data.
You probably want:
inotifywait \
--event create --event delete \
--event modify --event move \
--format "%e %w%f" \
--monitor \
--syslog --quiet --recursive \
/etc/haproxy |
while read CHANGED;
do
echo "$CHANGED"
haproxy -W -db -f /etc/haproxy/haproxy.cfg -p /var/run/haproxy.pid -sf $(cat /var/run/haproxy.pid) &
done
I am currently working on a Text-to-speech project and I need to write bash script which will, when it is called, execute two commands. If the first command returns the proper answer (if returns an answer at all), the second command will be called and executed.
My question is, how can I write a script, that executes shell commands in a specific certain file system location?
For example, I need to be in the directory /opt/text/example and execute this command:
sudo ./bin/sample_read -I ../languages/ -I ../languages -v dave -T 2 \
-i /opt/text/example.txt -F 22 -O embedded-pro -o out_file.pcm
and then to wait for the answer, then (if it is good) execute the second command.
The second command is
aplay -f S16_LE -r 22050 -c 1 out_file.pcm
This should help:
pushd /path/to/directory
my_var=$(command1)
if [ "$my_var" == "expected_result" ]; then
command2
fi
popd
You basically run command1 and store its output in my_var. Then you compare the content of $my_var with whatever you're expecting.
Also pushd <path>/popd allow you to move to a directory and back.
I currently use tail -f to monitor a log file: this way I get an autorefreshing console monitoring a web server.
Now, said webserver was moved to another host and I have no shell privileges for that.
Nevertheless I have a .txt network path, which in the end is a log file which is constantly updated.
So, I'd like to do something like tail -f, but on that url.
Would it be possible?In the end "in linux everything is a file" so..
You can do auto-refresh with help of watch combined with wget.
It won't show history, like tail -f, rather update screen like top.
Example of command, that shows content on file.txt on the screen, and update output every five seconds:
watch -n 5 wget -qO- http://fake.link/file.txt
Also, you can output n last lines, instead of the whole file:
watch -n 5 "wget -qO- http://fake.link/file.txt | tail"
In case if you still need behaviour like "tail -f" (with keeping history), I think you need to write a script that will download log file each time period, compare it to previous downloaded version, and then print new lines. Should be quite easy.
I wrote a simple bash script to fetch URL content each 2 seconds and compare with local file output.txt then append the diff to the same file
I wanted to stream AWS amplify logs in my Jenkins pipeline
while true; do comm -13 --output-delimiter="" <(cat output.txt) <(curl -s "$URL") >> output.txt; sleep 2; done
don't forget to create empty file output.txt file first
: > output.txt
view the stream :
tail -f output.txt
original comment : https://stackoverflow.com/a/62347827/2073339
UPDATE:
I found better solution using wget here:
while true; do wget -ca -o /dev/null -O output.txt "$URL"; sleep 2; done
https://superuser.com/a/514078/603774
I've made this small function and added it to the .*rc of my shell. This uses wget -c, so it does not re-download the whole page:
# Poll logs continuously over HTTP
logpoll() {
FILE=$(mktemp)
echo "———————— LOGPOLLING TO $FILE ————————"
tail -f $FILE &
tail_pid=$!
bg %1
stop=0
trap "stop=1" SIGINT SIGTERM
while [ $stop -ne 1 ]; do wget -co /dev/null -O $FILE "$1"; sleep 2; done
echo "——————————— LOGPOLL DONE ————————————"
kill $tail_pid
rm $FILE
trap - SIGINT SIGTERM
}
Explanation:
Create a temporary logfile using mktemp and save its path to $FILE
Make tail -f output the logfile continuously in the background
Make ctrl+c set stop to 1 instead of exiting the function
Loop until stop bit is set, i.e. until the user presses ctrl+c
wget given URL in a loop every two seconds:
-c - "continue getting partially downloaded file", so that wget continues instead of truncating the file and downloading again
-o /dev/null - wget's log messages shall be thrown into the void
-O $FILE - output the contents to the temp logfile we've created
Clean up after yourself: kill the tail -f, delete the temporary logfile, unset the signal handlers.
The proposed solutions periodically download the full file.
To avoid that I've created a package and published in NPM that does a HEAD request ( getting the size of the file ) and requesting only the last bytes.
Check it out and let me know if you need any help.
https://www.npmjs.com/package/#imdt-os/url-tail