Understanding the "extern" Keyword in C
By extern keyword, we mean external in C programming language. We will understand the extern keyword with a small example scenario where two variables must be accessed in two different files. In this case, the extern keyword comes handy. While defining a function or a variable in the C programming language, the memory is allocated for the variable, or the function declared.
It helps us extend the visibility of the functions and the variables in the C programming language; hence it is named as an external keyword in short read as an extern. Declaration of a variable or a function is no big deal, but allocating sufficient memory for them is a critical task, and the extern keyword is used in such problems.
Variables in C -1
Variables in C -2
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Variables in C -3
Compiles without any error
/usr/bin/ld: cannot open output file a.out: Permission denied collect2: error: ld returned one exit status
The below codes compile successfully and don't throw any errors when compiled.