Cross-Platform Header-Only C Utility to Get Process Memory Usage

Jul 25, 2025 c cpp memory

Easily retrieve the current memory usage of your C/C++ program in kilobytes, megabytes, or JSON—in a thread-safe and portable way.

What Is `memory_usage.h`?

memory_usage.h is a header-only, cross-platform C utility that lets you:

Get your program’s current memory usage
Use it in C or C++
Compile without linking external libraries (except psapi on Windows)
Avoid manual free() calls
Get memory output in KB, MB, or JSON format
Use it in multi-threaded programs safely

Features

Feature	Status
Linux Support	Yes
Windows Support	Yes
Header-only	Yes
No dynamic memory	Yes
Thread-safe	Yes (via `_Thread_local`)
Custom formatting	Yes (KB, MB, JSON)
C/C++ compatible	Yes

Header Code: `memory_usage.h`

How to Use

Example 1: Basic C Program

#include <stdio.h>
#include "memory_usage.h"

int main() {
    printf("Memory (KB): %s\n", get_memory_usage_str_kb());
    printf("Memory (MB): %s\n", get_memory_usage_str_mb());
    printf("Memory (JSON): %s\n", get_memory_usage_json());
    return 0;
}

Example 2: Thread Safety Test

#include <stdio.h>
#include <pthread.h>
#include "memory_usage.h"

void* thread_func(void* arg) {
    printf("Thread %ld: %s\n", (long)arg, get_memory_usage_str_kb());
    return NULL;
}

int main() {
    pthread_t t1, t2;
    pthread_create(&t1, NULL, thread_func, (void*)1);
    pthread_create(&t2, NULL, thread_func, (void*)2);
    pthread_join(t1, NULL);
    pthread_join(t2, NULL);
    return 0;
}

Compilation Instructions

Linux

Install dependencies (if needed):

sudo apt install build-essential

Compile:

gcc -o mem_test main.c -pthread

Run:

./mem_test

Expected output:

Memory (KB): 5672 KB
Memory (MB): 5.54 MB
Memory (JSON): {"memory_kb":5672,"memory_mb":5.54}

Windows

Requirements:

Windows 10 or later
MinGW (gcc) or Visual Studio

Using MinGW:

gcc -o mem_test.exe main.c -lpsapi
mem_test.exe

Using Visual Studio Developer Prompt:

cl /EHsc main.c /link psapi.lib

Output Example

Memory (KB): 12345 KB
Memory (MB): 12.06 MB
Memory (JSON): {"memory_kb":12345,"memory_mb":12.06}

Notes & Limitations

Aspect	Details
Thread safety	Depends on `_Thread_local` compiler support
Memory peak usage	Not yet implemented
Unsupported OS	Returns `"Unsupported OS"`
Reentrancy	Not reentrant (uses static buffer)
Embedded systems	Not supported (no `/proc`, no WinAPI)

Extensions You Can Add

Add peak memory (VmHWM: on Linux, PeakWorkingSetSize on Windows)
Output to a log file
Expose raw values via size_t get_memory_kb()
Track deltas over time (start/stop profiling)

Test It Yourself

gcc -o test main.c -pthread     # Linux
gcc -o test.exe main.c -lpsapi  # Windows

Conclusion

This simple, header-only memory tracking utility is a great tool for:

Debugging memory usage
Lightweight telemetry
Teaching and prototyping
Embedding in CLI tools

You don’t need to link to anything (except psapi on Windows), and it “just works” with clean and human-readable output.

License

You can consider it public domain / MIT-style. Use it freely in any project.

What Is memory_usage.h?