Read a value from INI text

Challenge

Look up a value in INI/conf text by [section] and key — stateful line parsing that drives countless tools' config loaders.

Task

Implement int ini_get(const char *ini, const char *section, const char *key, char *out, size_t cap) that finds the key=value line for key inside the [section] block and copies its value into out (NUL-terminated, bounded by cap).

Input

• ini: newline-separated config text with [section] headers and key=value lines.
• section: the section name to search within (without brackets).
• key: the key whose value you want (exact match).
• out / cap: destination buffer and its size.

Output

Return the length of the value written to out. Return -1 if the key isn't found in that section, the value doesn't fit in cap, or any pointer arg is NULL.

Example

ini = "[server]\nhost=localhost\nport=8080\n[auth]\nuser=admin\n"
ini_get(ini, "server", "host", out, 64)   ->   9,  out = "localhost"
ini_get(ini, "auth", "user", out, 64)      ->   5,  out = "admin"
ini_get(ini, "server", "user", out, 64)    ->   -1  (key is in [auth], not [server])

Edge cases

• Same key name in two sections: return the one in the requested section.
• Missing key, or section without that key: -1.

Rules

• Track the current section from [...] headers; match the key by exact length, not prefix. Bound the copy by cap.

Why this matters

INI/conf files drive countless tools. Looking up [section] key=value teaches stateful line parsing.

Input format

ini: config text. section/key: lookup target. out/cap: result buffer and size.

Output format

int length of the value copied to out, or -1 if not found / overflow / NULL.

Constraints

Stateful: track [section]; match keys exactly, only within the right section.

Starter code

#include <stddef.h>
int ini_get(const char *ini, const char *section, const char *key, char *out, size_t cap) {
    /* TODO */
    (void)ini; (void)section; (void)key; (void)out; (void)cap;
    return -1;
}

Common mistakes

Matching a key in the wrong section. Prefix-matching keys (use exact length). Forgetting the overflow guard.

Edge cases to handle

Same key in two sections. Missing key. Section with no such key.

Complexity

O(text length).

Background lessons

• Parsing CSV
• Log parsing — line iteration + classification

Up next

• Take the last N lines