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Using and Porting GNU Fortran

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15.1.7 Nothing Happens

It is occasionally reported that a "simple" program, such as a "Hello, World!" program, does nothing when it is run, even though the compiler reported no errors, despite the program containing nothing other than a simple PRINT statement.

This most often happens because the program has been compiled and linked on a UNIX system and named test, though other names can lead to similarly unexpected run-time behavior on various systems.

Essentially this problem boils down to giving your program a name that is already known to the shell you are using to identify some other program, which the shell continues to execute instead of your program when you invoke it via, for example:

 
sh# test
sh#

Under UNIX and many other system, a simple command name invokes a searching mechanism that might well not choose the program located in the current working directory if there is another alternative (such as the test command commonly installed on UNIX systems).

The reliable way to invoke a program you just linked in the current directory under UNIX is to specify it using an explicit pathname, as in:

 
sh# ./test
 Hello, World!
sh#

Users who encounter this problem should take the time to read up on how their shell searches for commands, how to set their search path, and so on. The relevant UNIX commands to learn about include man, info (on GNU systems), setenv (or set and env), which, and find.


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