I've just noticed GNU screen can run one command at a time, so this statement cannot work :
$ screen "command1 || command2"
but then this does not work either because GNU screen always returns 0 when it ends running command1 (even if command1 returns 1) :
$ screen command1 || screen command2
How to make GNU screen return the last return code to the shell when GNU screen ends ?
screen bash -c "command1 || command2"
Related
I had inotifywait working well, and suddenly it has stopped working as I expected. I'm not sure what's happening. My script:
#!/bin/bash
while inotifywait -e modify foo.txt; do
echo we did it
done
echo $?
When I execute it, I get:
Setting up watches.
Watches established.
When I edit foo.txt, I get:
0
And then the script exits.
Why is the while loop exiting given that the exit code is 0?
Why is it never echoing the content of the while loop?
UPDATE
This version does work. However I still don't get what's wrong with the original (given that, I swear, it was working for some time.)
#!/bin/bash
echo helle
while true; do
inotifywait -e modify foo.txt
echo hello
done
Ok, so I have this command that turns off my touchscreen. It works when I execute it in a root shell.
So this works:
sudo su
/usr/bin/echo $(ls /sys/bus/hid/drivers/hid-multitouch | awk NR==1'{print $1}') > /sys/bus/hid/drivers/hid-multitouch/unbind
And then my touchscreen stops working, which is the result that I wanted.
Now I want to make a touchscreen.service file to execute this on every boot. So in the service file I include:
ExecStart=/usr/bin/echo $(ls /sys/bus/hid/drivers/hid-multitouch | awk NR==1'{print $1}') > /sys/bus/hid/drivers/hid-multitouch/unbind
However it isn't working > nor throwing any errors that I've been able to catch.
I do know from earlier fidlings with .service files that I might actually need to use /usr/bin/sh -c, so I have also tried:
ExecStart=/usr/bin/sh -c "/usr/bin/echo $(ls /sys/bus/hid/drivers/hid-multitouch | awk NR==1'{print $1}') > /sys/bus/hid/drivers/hid-multitouch/unbind"
Yet this also doesn't work.. maybe because of the awk NR==1'{print $1}'part? I have also tried replacing it with awk NR==1'\''{print $1}'\''but again it fails to work.
Does anyone have any ideas on how to get the command that is working in my root cli environment to also work as a systemd service?
To start with,
The syntax of the awk command is just wrong. The quotes are incorrectly placed. The part NR == 1 is part of the awk command to indicate the first line record in the file, i.e.
awk NR==1'{print $1}'
# ^^^^^^^ should be within quotes
awk 'NR == 1 { print $1 }'
Your sequence of echo, ls and the command substitution $(..) doesn't look right. You are effectively echo-ing the literal string /sys/bus/hid/drivers/hid-multitouch (if ls finds the file at that path) over to the pipe and awk just writes that to the /sys/bus/hid/drivers/hid-multitouch/unbind file which might not be your desired action. You just needed to do run the command on the file directly as
awk 'NR == 1 { print $1 }' /sys/bus/hid/drivers/hid-multitouch > /sys/bus/hid/drivers/hid-multitouch/unbind
Now that, that the awk command is fixed, you have two options to run the above command as part of systemd, either put your command in a script or run the command directly. For putting it in a script refer to the Unix.SE answer Where do I put scripts executed by systemd units?. As for running the command directly in ExecStart. Aside from using /bin/sh also use the path /bin/awk
So putting it together and using /bin/ over /usr/bin, you can do below. This command uses ".." over awk script and needs escape of $1
ExecStart=/bin/sh -c '/bin/awk "NR == 1 { print \$1 }" /sys/bus/hid/drivers/hid-multitouch > /sys/bus/hid/drivers/hid-multitouch/unbind'
From some Googling (I'm no bash expert by any means) I was able to put together a bash script that allows me to run a test suite and output a status bar at the bottom while it runs. It typically takes about 10 hours, and the status bar tells me how many tests passed and how many failed.
It works great sometimes, however occasionally I will run into an infinite loop, which is bad (mmm-kay?). Here's the code I'm using:
#!/bin/bash
WHITE="\033[0m"
GREEN="\033[32m"
RED="\033[31m"
(run_test_suite 2>&1) | tee out.txt |
while IFS=read -r line;
do
printf "%$(tput cols)s\r" " ";
printf "%s\n" "$line";
printf "${WHITE}Passing Tests: ${GREEN}$(grep -c passed out.txt)\t" 2>&1;
printf "${WHITE}Failed Tests: ${RED}$( grep -c FAILED out.txt)${WHITE}\r" 2>&1;
done
What happens when I encounter the bug is I'll have an error message repeat infinitely, causing the log file (out.txt) to become some multi-megabyte monstrosity (I think it got into the GB's once). Here's an example error that repeats (with four lines of whitespace between each set):
warning caused by MY::Custom::Perl::Module::TEST_FUNCTION
print() on closed filehandle GEN3663 at /some/CPAN/Perl/Module.pm line 123.
I've tried taking out the 2>&1 redirect, and I've tried changing while IFS=read -r line; to while read -r line;, but I keep getting the infinite loop. What's stranger is this seems to happen most of the time, but there have been times I finish the long test suite without any problems.
EDIT:
The reason I'm writing this is to upgrade from a black & white test suite to a color-coded test suite (hence the ANSI codes). Previously, I would run the test suite using
run_test_suite > out.txt 2>&1 &
watch 'grep -c FAILED out.txt; grep -c passed out.txt; tail -20 out.txt'
Running it this way gets the same warning from Perl, but prints it to the file and moves on, rather than getting stuck in an infinite loop. Using watch, also prints stuff like [32m rather than actually rendering the text as green.
I was able to fix the perl errors and the bash script seems to work well now after a few modifications. However, it seems this would be a safer way to run the test suite in case something like that were to happen in the future:
#!/bin/bash
WHITE="\033[0m"
GREEN="\033[32m"
RED="\033[31m"
run_full_test > out.txt 2>&1 &
tail -f out.txt | while IFS= read line; do
printf "%$(tput cols)s\r" " ";
printf "%s\n" "$line";
printf "${WHITE}Passing Tests: ${GREEN}$(grep -c passed out.txt)\t" 2>&1;
printf "${WHITE}Failed Tests: ${RED}$( grep -c 'FAILED!!' out.txt)${WHITE}\r" 2>&1;
done
There are some downsides to this. Mainly, if I hit Ctrl-C to stop the test, it appears to have stopped, but really run_full_test is still running in the background and I need to remember to kill it manually. Also, when the test is finished tail -f is still running. In other words there are two processes running here and they are not in sync.
Here is the original script, slightly modified, which addresses those problems, but isn't foolproof (i.e. can get stuck in an infinite loop if run_full_test has issues):
#!/bin/bash
WHITE="\033[0m"
GREEN="\033[32m"
RED="\033[31m"
(run_full_test 2>&1) | tee out.txt | while IFS= read line; do
printf "%$(tput cols)s\r" " ";
printf "%s\n" "$line";
printf "${WHITE}Passing Tests: ${GREEN}$(grep -c passed out.txt)\t" 2>&1;
printf "${WHITE}Failed Tests: ${RED}$( grep -c 'FAILED!!' out.txt)${WHITE}\r" 2>&1;
done
The bug is in your script. That's not an IO error; that's an illegal argument error. That error happens when the variable you provide as a handle isn't a handle at all, or is one that you've closed.
Writing to a broken pipe results in the process being killed by SIGPIPE or in print returning false with $! set to EPIPE.
I'm making a script (Perl or shell) that launches a second Perl script. The script that it's launching has thousands of lines of output. So basically I want to make a script that launches another script without any output - and if possible run it within a screen session and then exit the script (yet keep the other running in the screen)? How can I do this?
When you launch your script direct output to /dev/null. To make a script run in the background use the & symbol. For example the follow will show nothing in the console and run in the background...
echo hi > /dev/null &
If you want to run in screen, you have to create a screenrc
#!/bin/sh
echo "screen my_perl_program" > /tmp/$$.screenrc
echo "autodetach on" >> /tmp/$$.screenrc
echo "startup_message off" >> /tmp/$$.screenrc
screen -L -dm -S session1 -c /tmp/$$.screenrc
Then you can restore it with screen -S session1
I know the perl one liner below is very simple, works and does a global substitution, A for a; but how do I run it in a makefile?
perl -pi -e "s/a/A/g" filename
I have tried (I now think the rest of the post is junk as the shell command does a command line expansion - NOT WHAT I WANT!) The question above still stands!
APP = $(shell perl -pi -e "s/a/A/g" filename)
with and without the following line
EXE = $(APP)
and I always get the following error
make: APP: Command not found
which I assume comes from the line that starts APP
Thanks
If you want to run perl as part of a target's action, you might use
$ cat Makefile
all:
echo abc | perl -pe 's/a/A/g'
$ make
echo abc | perl -pe 's/a/A/g'
Abc
(Note that there's a TAB character before echo.)
Perl's -i option is for editing files in-place, but that will confuse make (unless perhaps you're writing a phony target). A more typical pattern is to make targets from sources. For example:
$ cat Makefile
all: bAr
bAr: bar.in
perl -pe 's/a/A/g' bar.in > bAr
$ cat bar.in
bar
$ make
perl -pe 's/a/A/g' bar.in > bAr
$ cat bAr
bAr
If you let us know what you're trying to do, we'll be able to give you better, more helpful answers.
You should show the smallest possible Makefile which demonstrates your problem, and show how you are calling it. Assuming your Makefile looks something like this, I get the error message. Note that there is a tab character preceding the APP in the all: target.
APP = $(shell date)
all:
APP
Perhaps you meant to do this instead:
APP = $(shell date)
all:
$(APP)
I did not use your perl command because it does not run for me as-is.
Do you really mean to use Perl's substitution operator? perl -pi -e "s/a/A/g"
Here is a link to GNU make documentation.