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I have a file database/seed.js that performs an async insertion into a database.

If I run node database/seed.js && mongo < ./database/updateCounter.js, am I guaranteed that mongo < ./database/updateCounter.js will run after the async insertion is fully complete?

This answer says A && B means B will only run if A was successful, but how is success determined?

Success is determined by the exit status of the command.

Each linux process when terminates returns a integer called exit status. This is the number you usually see in the statements return 0 in most programming languages.

From bash manual 3.2.3 List of Commands:

An AND list has the form

command1 && command2

command2 is executed if, and only if, command1 returns an exit status of zero.

Exit status equal to zero usually means success and nonzero exit status means failure. Like in case of grep - exit status equal to 0 means pattern was found in file/stream, exit status of grep equal to 1 means no pattern was found in file/stream. There are two simple programs in bash or shell builtins - true and false, the first returns status 0 and the other returns with status 1. This is opposed to boolean values in programming languages - usually true is defined as having nonzero value, usually 1, and false is defined as equal to zero.

In your question there is used the word "async" which indicates that the action takes place asynchronously. Usually means that the action has started or is requested to start, but may or may not have finished and with what result. I don't know what database/seed.js does and how it works - inspect it and refer to it to know what exit status it sets on which conditions.

But if you run node database/seed.js && mongo < ./database/updateCounter.js you are "guaranteed" that mongo program will execute if, and only if, the node program has terminated with exit status of zero. I quoted "guaranteed", because noone guarantees you that in any way - bash is licensed under GNU General Public License and you can read in the license clearly that:

15. Disclaimer of Warranty.
    
    THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.