If one has POSIX extensions available, then it seems that defining _POSIX_C_SOURCE and just using getline or detdelim is the way to go. However, for source that is just C, here is a solution I've found from various sources, mainly [here](https://stackoverflow.com/questions/16870485/how-can-i-read-an-input-string-of-unknown-length). I've also tried to make it more safe. ``` // Read line from stdin #include <stdio.h> #include <stdlib.h> #define CHUNK_SIZE 16 // Allocate memory in chunks of this size // Safe self-realloc void *xrealloc(void *ptr, size_t size) { void *tmp = realloc(ptr, size); if (!tmp) free(ptr); return tmp; } // Dynamically allocate memory for char pointer from stdin char *readline(void) { size_t len = 0, chunk = CHUNK_SIZE; char *str = (char *)malloc(CHUNK_SIZE); if (!str) return NULL; int ch; while((ch = getchar()) != EOF && ch != '\n' && ch != '\r') { str[len++] = ch; if (len == chunk) { str = (char *)xrealloc(str, chunk+=CHUNK_SIZE); if (!str) return NULL; } } str[len++] = '\0'; // Ensure str is null-terminated return (char *)xrealloc(str, len); } int main(void) { setbuf(stdout, NULL); // Ensure environment doesn't buffer stdout printf("Enter name: "); char *userName = readline(); if (!userName) return 1; printf("Hello, %s!\n", userName); free(userName); return 0; } ``` The idea is that we allocate in chunks of 16, or whichever size. xrealloc is handy when reallocating a block of memory to itself. ``` int *ptr = malloc(sizeof(int) * 4); ptr = (int *)realloc(ptr, sizeof(int) * 8); ``` If realloc fails, ptr gets assigned `NULL`, and we lose the address that we need to free, causing a memory leak. So, xrealloc allows for safe self re-allocation.