If I have a UNIX shell script which has some program on each line that needs to be run, like
#!/bin/bash
command1
command2
command3
command4
will command2 execute only after command1 execution finishes or are they run in parallel without waiting for the previous command to finish as each command is a separate process that needs to be executed.
The commands are run serially. To run them in parallel, append & to each line:
#!/bin/bash
command1&
command2&
command3&
command4&
wait
Related
Two bash scripts, A and script B
how to schedule cron to run script B after successful execution of script A.
***** /home/scripts/A.sh ; /home/scripts/B.sh
Above one will run simultaneously but i should run B.sh after script A finish execution successfully
command1 && command2
command2 would only be run, if command1 returns an exit status of zero.
In Jenkins, I have created a job which runs many shell script commands:
command1
command2
...etc
command1 is an ssh command which calls a shell script file on another server machine. I have to wait until it is finished, and AFTER it, command2 should come.
So, how can I make sure that the script file on the other machine, started by command1, has already finished its jobs, when in the Jenkins job the next command (command2) is started?
Or, alternatively,how can I make sure that command2 won't be started until the shell script on the other machine (started by command1) has already finished?
You can check out "How to send many commands to shell and wait for the command behind ends" in order to chain commands and wait for their completion.
When you execute a command through an ssh session, you might have to wrap that command in a script able to loop/wait for the command completion.
See an example in "How can I make ssh wait until the command exits?".
Or (a simpler wraper): How do I know when a command run over ssh has finished?
#/bin/bash
$#
echo "==== Command Output Finished ===="
look for the string ==== Command Output Finished ==== in your I/O routines to determine where the boundary between command outputs are.
Or you can try isolate those commands in their own Jenkins shell build step.
(Not a different job, just a different build step within the same job)
I have used nohup command and execute a unix shell script from background but i want to execute the next command immediately before the previous shell script gets completed , i do not want to wait until and unless the shell script gets completed.
Is there any way , i tried with nohup but i m getting this:
nohup: appending output to `nohup.out'
and not getting control to run the next command. Is there any way to exit immediatley after calling a shell script and let it run in the background , execute the next command without using CTRL+C or force shutdown.
I have used the below command but
$ nohup sh dataload.sh &
[1] 14472
$ nohup: appending output to `nohup.out'
here I am not able to get the control to execute the next command
Just put it in the background: nohup your_command &
If I have a UNIX shell script which has some commands on each line that needs to be run, like
#!/bin/bash
command1
command2
command2 to be excuted only after completion of command1. how to achieve it
You've already done it. bash normally waits for each command to run before running the next command. If you end the command with an ampersand (&), then it runs the command in the background, but since you haven't done that, each command runs synchronously.
Do lines in a bash script execute sequentially? I can't see any reason why not, but I am really new to bash scripting and I have a couple commands that need to execute in order.
For example:
#!/bin/sh
# will this get finished before the next command starts?
./someLongCommand1 arg1
./someLongCommand2 arg1
Yes, they are executed sequentially. However, if you run a program in the background, the next command in your script is executed immediately after the backgrounded command is started.
#!/bin/sh
# will this get finished before the next command starts?
./someLongCommand1 arg1 &
./someLongCommand2 arg1 &
would result in an near-instant completion of the script; however, the commands started in it will not have completed. (You start a command in the background by putting an ampersand (&) behind the name.
Yes... unless you go out of your way to run one of the commands in the background, one will finish before the next one starts.