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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
Old 01-23-2018
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
 

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LIBBASH(7)							  libbash Manual							LIBBASH(7)

NAME
libbash -- A bash shared libraries package. DESCRIPTION
libbash is a package that enables bash dynamic-like shared libraries. Actually its a tool for managing bash scripts whose functions you may want to load and use in scripts of your own. It contains a 'dynamic loader' for the shared libraries ( ldbash(1)), a configuration tool (ldbashconfig(8)), and some libraries. Using ldbash(1) you are able to load loadable bash libraries, such as getopts(1) and hashstash(1). A bash shared library that can be loaded using ldbash(1) must answer 4 requirments: 1. It must be installed in $LIBBASH_PREFIX/lib/bash (default is /usr/lib/bash). 2. It must contain a line that begins with '#EXPORT='. That line will contain (after the '=') a list of functions that the library exports. I.e. all the function that will be usable after loading that library will be listed in that line. 3. It must contain a line that begins with '#REQUIRE='. That line will contain (after the '=') a list of bash libraries that are required for our library. I.e. every bash library that is in use in our bash library must be listed there. 4. The library must be listed (For more information, see ldbashconfig(8)). Basic guidelines for writing library of your own: 1. Be aware, that your library will be actually sourced. So, basically, it should contain (i.e define) only functions. 2. Try to declare all variables intended for internal use as local. 3. Global variables and functions that are intended for internal use (i.e are not defined in '#EXPORT=') should begin with: __<library_name>_ For example, internal function myfoosort of hashstash library should be named as __hashstash_myfoosort This helps to avoid conflicts in global name space when using libraries that come from different vendors. 4. See html manual for full version of this guide. AUTHORS
Hai Zaar <haizaar@haizaar.com> Gil Ran <ril@ran4.net> SEE ALSO
ldbash(1), ldbashconfig(8), getopts(1), hashstash(1) colors(1) messages(1) urlcoding(1) locks(1) Linux Epoch Linux
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