linux - How to have bash shell not execute rest of semicolon list of commands? -


suppose following in bash @ command prompt:

cmd1;cmd2;cmd3

if cmd1 fails how bash not cmd2.

cmd1 && cmd2 && cmd3

explanation

execute cmd1. if fails, cmd2 , cmd3 not executed.

why? because false logically anded else equal false, if cmd1 returns false there no need evaluate cmd2 , cmd3. , reasoning, if cmd1 succeeds , cmd2 fails, don't execute cmd3.

note

just make things little more confusing, posix systems (like linux , other unix variants) return 0 success , non-zero failure.

so, when failure above

  • false = non-zero = failure

  • true = zero = success

why? because numerical value of return code used indicate different failure codes.

for example,

$ ls /root ls: cannot open directory /root: permission denied $ echo $?  2 $ asdf asdf: command not found... $ echo $? 127 $ ls / bin  boot  data  dev  etc  home  lib  ... $ echo $? 0

ls returns "1" minor problems , "2" more serious problems. bash shell returns "127" indicate "command not found", , ls / returns "0" indicate success.


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