C Reference Cheat Sheet (Page 5 of 13) in pdf

C Reference Cheat Sheet

Ashlyn Black

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Functions

Functions (cont)

Declaring

Returning an array/string/structure by pointer.

type f(){ static

The static qualifier is necessary otherwise

type x[]; return

type/void funcName([args...]){ [return var;] }

x won't exist after the function exits.

&x; }

Function names follow the same restrictions as variable names but must

Passing by pointer allows you to change the originating variable within the

also be unique.

function.

Return value type (void if none.)

type/void

Scope

Function name and argument parenthesis.

funcName()

int f(){ int i = 0; } i++; 

Argument types & names (void if none.)

args...

i is declared inside f(), it doesn't exist outside that function.

Function content delimi t ers.

{}

Prototyping

Value to return to function call origin. Skip for void

return var;

type funcName(args...);

type functions. Functions exit immediately after a

Place before declaring or referencing respective function (usually before

return.

main.)

By Value vs By Pointer

Same type, name and args... as

type

Passing variable y to function f argument x (by

void f(type

respective function.

funcName([args...])

value.)

x); f(y);

Semicolon instead of function delimiters.

;

Passing an array/string to function f argument x (by

void f(type

pointer.)

*x);

main()

f(array);

int main(int argc, char *argv[]){return int;}

Passing a structure to function f argument x (by

void f(type

pointer.)

Anatomy

*x);

f(structure);

Program entry point.

int main

Passing variable y to function f argument x (by

void f(type

# of command line arguments.

int argc

pointer.)

*x); f( &y);

Command line arguments in an array of strings. #1 is

char *argv[]

Returning by value.

always the program filename.

type f(){

return x; }

Exit status (inte g er) returned to the OS upon

return int;

program exit.

Returning a variable by pointer.

type f(){ type

Command Line Arguments

x; return &x;

}

Three arguments, "ap p ", "tw o " and "3".

app two 3

Two arguments, "ap p " and "two 3".

app "two 3"

main is the first function called when the program executes.

By Ashlyn Black

Published 28th January, 2015.

C Reference Cheat Sheet Page 5

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