How to run several bash commands put in bash command line? Post: 303011747

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Top Forums Shell Programming and Scripting How to run several bash commands put in bash command line? Post 303011747 by rbatte1 on Tuesday 23rd of January 2018 06:11:47 AM

01-23-2018

Moderator

What you originally have is more like saying "Run echo ${PATH} in the background and (ignoring if it works or not) run echo have a nice day! in the foreground"

Your output may not always be consistent. In this very simple case it probably always will be but more complex calls could have the output from either displayed first or even interleaved if you have two long running processes that output multiple lines. Can you tell us what you are trying to achieve here?

If you have a cmd1 ; cmd2 ; cmd3, these run sequentially. There is no return code checking done, it just runs one after the other.

If you have a cmd1 & cmd2 & cmd3 &, these run in the background (so disconnected from your STDIN (usually keyboard) and may independently write output to STDOUT (usually screen) ) and because cmd3 has a trailing & putting it in the background, you get dropped back to the shell (or calling program) and can carry on with other work. This may or may not be what you wanted.

If you have a mixture then you have to interpret what will happen. You can also add conditional execution, so cmd1 && cmd2 || cmd3 will run cmd1. If there is a zero return code (deemed as success) then run cmd2. If either cmd1 or cmd2 have a non-zero return code (deemed as a failure) then run cmd3

This can be quite compact but often can get complicated to interpret, so most people a re more explicit with something more like:

Code:

cmd1
RC=$?
if [ $RC -eq 0 ]
then
   cmd2
   RC=$?
fi

if [ $RC -ne 0 ]
then
   cmd3
fi

Does this help, or just confuse? Apologies if it is the latter.

Robin

rbatte1

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LEARN ABOUT X11R4

shell

shell(1F)							   FMLI Commands							 shell(1F)

NAME

       shell - run a command using shell

SYNOPSIS

       shell command [command] ...

DESCRIPTION

       The  shell  function  concatenate  its arguments, separating each by a space, and passes this string to the shell ($SHELL if set, otherwise
       /usr/bin/sh).

EXAMPLES

       Example 1: A sample output of shell command.

       Since the Form and Menu Language does not directly support background processing, the shell function can be used instead.

       `shell "build prog > /dev/null &"`

       If you want the user to continue to be able to interact with the application while the background job is running, the  output  of  an  exe-
       cutable	run  by shell in the background must be redirected: to a file if you want to save the output, or to /dev/null if you don't want to
       save it (or if there is no output), otherwise your application may appear to be hung until the background job finishes processing.

       shell can also be used to execute a command that has the same name as an FMLI built-in function.

NOTES

       The arguments to shell will be concatenate using spaces, which may or may not do what is expected. The variables set in local  environments
       will not be expanded by the shell because "local" means "local to the current process."

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       sh(1), attributes(5)

SunOS 5.10							    5 Jul 1990								 shell(1F)

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