C Cheatsheet: Common Functions

Cheatsheet: Common Functions

I/O (<stdio.h>)

• printf(format, ...)
• scanf(format, &var)
• puts(str) - string + newline
• fgets(buf, size, file) - safe line read
• fopen(name, "r") - open a file

Strings (<string.h>)

• strlen(s) - length
• strcpy(d, s) - copy string
• strcat(d, s) - append
• strcmp(a, b) - compare (0 = equal)

Memory (<stdlib.h>)

• malloc(size) - allocate
• free(ptr) - release
• calloc(n, size) - zeroed allocate
• realloc(p, size) - resize

Math (<math.h>)

• pow(x, y) - power
• sqrt(x) - square root
• fabs(x) - absolute (float)
• abs(x) - absolute (int)

TL;DR

• <string.h> for str functions.
• <stdlib.h> for malloc/free.
• <math.h> for math funcs.