I am trying to create one wrapper script to trigger the parent script at 6AM only. But it is not properly working. It always showing Do Nothing and else part is looping without exit. Can any one help?
I want to check if the time is 6 AM and also need to check the string from text file(status). if both conditions are satisfied my parent script should execute via this wrapper script.
Below is the script
path= $(cat /home/avj/)
mode= $(cat /home/avj/status)
checktime="060000"
echo $checktime
echo $currentTime
while true
do
currentTime=date +"%H%M%S"
if [[ $currentTime -eq $checktime && $status == running ]];
then
sh &path/parent.sh
else
echo Do Nothing
fi
done
Usually on Linux, you use crontab for this kind of scduled tasks. But you have to specify the time when you "set up the timer" - so if you want it to be configured in the file itself, you will have to create some mechanism for this.
For example, you can add crontab
30 1 * * 5 /path/to/script/script.sh
Will execute the script every Friday at 1: 30 (AM) here:
30 is minutes
1 is an hour
the next 2 * are the day of month and month (in that order), and the 5th is the day of the week
I'm trying to schedule my script to run at two different times and then keep running in the background waiting for the next time that the conditions are met again.
So far I am not able to do it because after that one condition is met this scripts exits automatically:
function schedule {
while :
do
hour=$(date +"%H")
minute=$(date +"%M")
if [[ "$hour" = "02" && "$minute" = "31" ]]; then
# run some script
exec /home/gfx/Desktop/myscript.sh
wait
schedule
elif [[ "$hour" = "02" && "$minute" = "32" ]]; then
# run some script
exec /home/gfx/Desktop/myscript.sh
wait
schedule
fi
done
}
schedule
The script that I execute is the following :
$cat myscript.sh
echo "this a message"
Any idea or comment are welcome, thanks!
When you do:
exec some program
something else
if the exec works, then the something else will never happen because the script is replaced by what you exec'd
Maybe instead of:
exec /home/gfx/Desktop/myscript.sh
wait
schedule
you want:
/home/gfx/Desktop/myscript.sh &
wait
# schedule -- don't make a fork bomb
As noted in the comments, & + wait is kind of silly, you probably want:
/home/gfx/Desktop/myscript.sh &
# wait
# schedule
or:
/home/gfx/Desktop/myscript.sh
# wait
# schedule
depending on whether or not you want myscript in the background.
ALSO you should put a sleep in the loop, (maybe sleep(59)) to keep it from looping like a banshee.
You begin to understand the appeal of cron I think (at least for things you don't want to interact with your terminal session).
Crontabs are best place to put these things.
Edit crontab using
$ crontab -e
Add following lines to the files
31 2 * * * /home/gfx/Desktop/myscript.sh
And save crontab file. Your script will be executed every day 2:31 am
I am having a problem getting bash to do exactly what I want, it's not a major issue, but annoying.
1.) I have a third party software I run that produces some output as stderr. Some of it is useful, some of it is regularly stuff I don't care about and I don't want this dumped to screen, however I do want the useful parts of the stderr dumped to screen. I figured the best way to achieve this was to pass stderr to a function, then use conditions in that function to either show the stderr or not.
2.) This works fine. However the solution I have implemented dumped out my errors at the right time, but then returns a bash prompt and I want to summarise the status of the errors at the end of the function, but echo-ing here prints the text after the prompt meaning that I have to press enter to get back to a clean prompt. It shall become clear with the example below.
My error stream generator:
./TestErrorStream.sh
#!/bin/bash
echo "test1" >&2
My function to process this:
./Function.sh
#!/bin/bash
function ProcessErrors()
{
while read data;
do
echo Line was:"$data"
done
sleep 5 # This is used simply to simulate the processing work I'm doing on the errors.
echo "Completed"
}
I source the Function.sh file to make ProcessErrors() available, then I run:
2> >(ProcessErrors) ./TestErrorStream.sh
I expect (and want) to get:
user#user-desktop:~/path$ 2> >(ProcessErrors) ./TestErrorStream.sh
Line was:test1
Completed
user#user-desktop:~/path$
However what I really get is:
user#user-desktop:~/path$ 2> >(ProcessErrors) ./TestErrorStream.sh
Line was:test1
user#user-desktop:~/path$ Completed
And no clean prompt. Of course the prompt is there, but "Completed" is being printed after the prompt, I want to printed before, and then a clean prompt to appear.
NOTE: This is a minimum working example, and it's contrived. While other solutions to my error stream problem are welcome I also want to understand how to make bash run this script the way I want it to.
Thanks for your help
Joey
Your problem is that the while loop stay stick to stdin until the program exits.
The release of stdin occurs at the end of the "TestErrorStream.sh", so your prompt is almost immediately available compared to what remains to process in the function.
I suggest you wrap the command inside a script so you'll be able to handle the time you want before your prompt is back (I suggest 1sec more than the suspected time needed for the function to process the remaining lines of codes)
I successfully managed to do this like that :
./Functions.sh
#!/bin/bash
function ProcessErrors()
{
while read data;
do
echo Line was:"$data"
done
sleep 5 # simulate required time to process end of function (after TestErrorStream.sh is over and stdin is released)
echo "Completed"
}
./TestErrorStream.sh
#!/bin/bash
echo "first"
echo "firsterr" >&2
sleep 20 # any number here
./WrapTestErrorStream.sh
#!/bin/bash
source ./Functions.sh
2> >(ProcessErrors) ./TestErrorStream.sh
sleep 6 # <= this one is important
With the above you'll get a nice "Completed" before your prompt after 26 seconds of processing. (Works fine with or without the additional "time" command)
user#host:~/path$ time ./WrapTestErrorStream.sh
first
Line was:firsterr
Completed
real 0m26.014s
user 0m0.000s
sys 0m0.000s
user#host:~/path$
Note: the process substitution ">(ProcessErrors)" is a subprocess of the script "./TestErrorStream.sh". So when the script ends, the subprocess is no more tied to it nor to the wrapper. That's why we need that final "sleep 6"
#!/bin/bash
function ProcessErrors {
while read data; do
echo Line was:"$data"
done
sleep 5
echo "Completed"
}
# Open subprocess
exec 60> >(ProcessErrors)
P=$!
# Do the work
2>&60 ./TestErrorStream.sh
# Close connection or else subprocess would keep on reading
exec 60>&-
# Wait for process to exit (wait "$P" doesn't work). There are many ways
# to do this too like checking `/proc`. I prefer the `kill` method as
# it's more explicit. We'd never know if /proc updates itself quickly
# among all systems. And using an external tool is also a big NO.
while kill -s 0 "$P" &>/dev/null; do
sleep 1s
done
Off topic side-note: I'd love to see how posturing bash veterans/authors try to own this. Or perhaps they already did way way back from seeing this.
I am very new to shell scripting.
The script should fire a command if the given time as command line argument is equal to the system time, else it should wait(poll) for the given time.
I started with very basics, but i am stuck here only:-(
#!/bin/sh
now=$(date +%k%M)
cur="055" # should be given as command line arg
if ($now == $cur)
then
echo "Fire command here"
else
echo "poll for time"
fi
When i execute the script:
./script.sh: line 5: 055: command not found
poll for time
Thanks for the help.
I think the above is just a small syntax error, instead of:
if ($now == $cur)
You may want to do this:
if [ $now -eq $cur ] #very basic comparison here, you may want to have a
#look at the bash comparisons
Update
Could you change the variable to,
$cur=$(date +%H%M)
And in case the input is not provided by you, you should remove the space in front
of the $now
now=$(echo $now | sed 's/\s//g') #this removes the spaces in the input
You can run a program # a particular time with :
crontab -e
and
0 14 * * * command
to run command # 14 PM (by example)
begin="`date '+%s'`"
final=... #should be converted to seconds since epoch...
sleep $((final - begin))
exec_your_command
The problem you described seems to be exactly what crontab is designed to handle, from wikipedia "Cron is driven by a crontab (cron table) file, a configuration file that specifies shell commands to run periodically on a given schedule."
Here is a quick reference, it is reletively barebones, but should be enough to determine if it meets your needs.
Use following code
if [ $now == $cur ]
When I use exit command in a shell script, the script will terminate the terminal (the prompt). Is there any way to terminate a script and then staying in the terminal?
My script run.sh is expected to execute by directly being sourced, or sourced from another script.
EDIT:
To be more specific, there are two scripts run2.sh as
...
. run.sh
echo "place A"
...
and run.sh as
...
exit
...
when I run it by . run2.sh, and if it hit exit codeline in run.sh, I want it to stop to the terminal and stay there. But using exit, the whole terminal gets closed.
PS: I have tried to use return, but echo codeline will still gets executed....
The "problem" really is that you're sourcing and not executing the script. When you source a file, its contents will be executed in the current shell, instead of spawning a subshell. So everything, including exit, will affect the current shell.
Instead of using exit, you will want to use return.
Yes; you can use return instead of exit. Its main purpose is to return from a shell function, but if you use it within a source-d script, it returns from that script.
As §4.1 "Bourne Shell Builtins" of the Bash Reference Manual puts it:
return [n]
Cause a shell function to exit with the return value n.
If n is not supplied, the return value is the exit status of the
last command executed in the function.
This may also be used to terminate execution of a script being executed
with the . (or source) builtin, returning either n or
the exit status of the last command executed within the script as the exit
status of the script.
Any command associated with the RETURN trap is executed
before execution resumes after the function or script.
The return status is non-zero if return is used outside a function
and not during the execution of a script by . or source.
You can add an extra exit command after the return statement/command so that it works for both, executing the script from the command line and sourcing from the terminal.
Example exit code in the script:
if [ $# -lt 2 ]; then
echo "Needs at least two arguments"
return 1 2>/dev/null
exit 1
fi
The line with the exit command will not be called when you source the script after the return command.
When you execute the script, return command gives an error. So, we suppress the error message by forwarding it to /dev/null.
Instead of running the script using . run2.sh, you can run it using sh run2.sh or bash run2.sh
A new sub-shell will be started, to run the script then, it will be closed at the end of the script leaving the other shell opened.
Actually, I think you might be confused by how you should run a script.
If you use sh to run a script, say, sh ./run2.sh, even if the embedded script ends with exit, your terminal window will still remain.
However if you use . or source, your terminal window will exit/close as well when subscript ends.
for more detail, please refer to What is the difference between using sh and source?
This is just like you put a run function inside your script run2.sh.
You use exit code inside run while source your run2.sh file in the bash tty.
If the give the run function its power to exit your script and give the run2.sh
its power to exit the terminator.
Then of cuz the run function has power to exit your teminator.
#! /bin/sh
# use . run2.sh
run()
{
echo "this is run"
#return 0
exit 0
}
echo "this is begin"
run
echo "this is end"
Anyway, I approve with Kaz it's a design problem.
I had the same problem and from the answers above and from what I understood what worked for me ultimately was:
Have a shebang line that invokes the intended script, for example,
#!/bin/bash uses bash to execute the script
I have scripts with both kinds of shebang's. Because of this, using sh or . was not reliable, as it lead to a mis-execution (like when the script bails out having run incompletely)
The answer therefore, was
Make sure the script has a shebang, so that there is no doubt about its intended handler.
chmod the .sh file so that it can be executed. (chmod +x file.sh)
Invoke it directly without any sh or .
(./myscript.sh)
Hope this helps someone with similar question or problem.
To write a script that is secure to be run as either a shell script or sourced as an rc file, the script can check and compare $0 and $BASH_SOURCE and determine if exit can be safely used.
Here is a short code snippet for that
[ "X$(basename $0)" = "X$(basename $BASH_SOURCE)" ] && \
echo "***** executing $name_src as a shell script *****" || \
echo "..... sourcing $name_src ....."
I think that this happens because you are running it on source mode
with the dot
. myscript.sh
You should run that in a subshell:
/full/path/to/script/myscript.sh
'source' http://ss64.com/bash/source.html
It's correct that sourced vs. executed scripts use return vs. exit to keep the same session open, as others have noted.
Here's a related tip, if you ever want a script that should keep the session open, regardless of whether or not it's sourced.
The following example can be run directly like foo.sh or sourced like . foo.sh/source foo.sh. Either way it will keep the session open after "exiting". The $# string is passed so that the function has access to the outer script's arguments.
#!/bin/sh
foo(){
read -p "Would you like to XYZ? (Y/N): " response;
[ $response != 'y' ] && return 1;
echo "XYZ complete (args $#).";
return 0;
echo "This line will never execute.";
}
foo "$#";
Terminal result:
$ foo.sh
$ Would you like to XYZ? (Y/N): n
$ . foo.sh
$ Would you like to XYZ? (Y/N): n
$ |
(terminal window stays open and accepts additional input)
This can be useful for quickly testing script changes in a single terminal while keeping a bunch of scrap code underneath the main exit/return while you work. It could also make code more portable in a sense (if you have tons of scripts that may or may not be called in different ways), though it's much less clunky to just use return and exit where appropriate.
Also make sure to return with expected return value. Else if you use exit when you will encounter an exit it will exit from your base shell since source does not create another process (instance).
Improved the answer of Tzunghsing, with more clear results and error re-direction, for silent usage:
#!/usr/bin/env bash
echo -e "Testing..."
if [ "X$(basename $0 2>/dev/null)" = "X$(basename $BASH_SOURCE)" ]; then
echo "***** You are Executing $0 in a sub-shell."
exit 0
else
echo "..... You are Sourcing $BASH_SOURCE in this terminal shell."
return 0
fi
echo "This should never be seen!"
Or if you want to put this into a silent function:
function sExit() {
# Safe Exit from script, not closing shell.
[ "X$(basename $0 2>/dev/null)" = "X$(basename $BASH_SOURCE)" ] && exit 0 || return 0
}
...
# ..it have to be called with an error check, like this:
sExit && return 0
echo "This should never be seen!"
Please note that:
if you have enabled errexit in your script (set -e) and you return N with N != 0, your entire script will exit instantly. To see all your shell settings, use, set -o.
when used in a function, the 1st return 0 is exiting the function, and the 2nd return 0 is exiting the script.
if your terminal emulator doesn't have -hold you can sanitize a sourced script and hold the terminal with:
#!/bin/sh
sed "s/exit/return/g" script >/tmp/script
. /tmp/script
read
otherwise you can use $TERM -hold -e script
If a command succeeded successfully, the return value will be 0. We can check its return value afterwards.
Is there a “goto” statement in bash?
Here is some dirty workaround using trap which jumps only backwards.
#!/bin/bash
set -eu
trap 'echo "E: failed with exitcode $?" 1>&2' ERR
my_function () {
if git rev-parse --is-inside-work-tree > /dev/null 2>&1; then
echo "this is run"
return 0
else
echo "fatal: not a git repository (or any of the parent directories): .git"
goto trap 2> /dev/null
fi
}
my_function
echo "Command succeeded" # If my_function failed this line is not printed
Related:
https://stackoverflow.com/a/19091823/2402577
How to use $? and test to check function?
I couldn't find solution so for those who want to leave the nested script without leaving terminal window:
# this is just script which goes to directory if path satisfies regex
wpr(){
leave=false
pwd=$(pwd)
if [[ "$pwd" =~ ddev.*web ]]; then
# echo "your in wordpress instalation"
wpDir=$(echo "$pwd" | grep -o '.*\/web')
cd $wpDir
return
fi
echo 'please be in wordpress directory'
# to leave from outside the scope
leave=true
return
}
wpt(){
# nested function which returns $leave variable
wpr
# interupts the script if $leave is true
if $leave; then
return;
fi
echo 'here is the rest of the script, executes if leave is not defined'
}
I have no idea whether this is useful for you or not, but in zsh, you can exit a script, but only to the prompt if there is one, by using parameter expansion on a variable that does not exist, as follows.
${missing_variable_ejector:?}
Though this does create an error message in your script, you can prevent it with something like the following.
{ ${missing_variable_ejector:?} } 2>/dev/null
1) exit 0 will come out of the script if it is successful.
2) exit 1 will come out of the script if it is a failure.
You can try these above two based on ur req.