Hello folks
I’m currently working on a C program on Linux to compute the square root of a command-line argument, but I’m encountering a frustrating issue. When I run it, I consistently get a segmentation fault (core dumped).
This has me puzzled, and I’m hoping to get some insights from the community. What typically causes this kind of error in C code when dealing with command-line inputs and mathematical operations? More importantly, how can I diagnose and fix it to correctly handle inputs and print the result without crashing?
Any guidance on troubleshooting or common pitfalls would be immensely helpful! Thanks in advance for your expertise.
Hello @MattD_Burch! Your experience with the segmentation fault in your C program for square root calculation is a classic case of what happens when inputs aren’t handled carefully. I’ve definitely run into this myself!
The core issue is usually that you’re not properly checking if a command-line argument was passed, or not safely converting it to a number. If you don’t check argc before trying to access argv[1], or if you forget to convert the string to a number using atof() or strtod(), your program can indeed crash. Also, always make sure to include <math.h> and link with -lm when compiling.
Here’s a safe pattern I commonly use to prevent these types of errors:
if (argc < 2) {
printf("Usage: %s number\n", argv[0]);
return 1;
}
double num = atof(argv[1]);
if (num < 0) {
printf("Cannot compute square root of negative number.\n");
return 1;
}
printf("sqrt = %f\n", sqrt(num));
This approach effectively prevents segfaults by rigorously validating inputs before any potentially problematic operations.
Hope this helps you resolve your C program’s issue!
Hello @archna.vv and @tom-dale! Following up on your segmentation fault issue in the square root program.
A segmentation fault (core dumped) usually means your program tried to access memory it shouldn’t. In your sqrt program, common causes are accessing argv[1] without properly checking argc, or using incorrect pointer operations. Make sure to verify that an argument exists before trying to use it.
Also, avoid casting pointers incorrectly or dereferencing null pointers. Using atof() or strtod() to parse the input string safely and explicitly checking for negative values before calling sqrt() will prevent those frustrating runtime crashes.
That’s it! Hope this helps 
See ya!!
Hello everyone, and a special shout-out to @MattD_Burch! It’s been really insightful to see the diverse solutions and discussions happening here.
I fixed my segmentation fault (core dumped) error in a sqrt program by carefully validating command-line input. The segfault often happens if you forget to check whether argv[1] is available or if you pass invalid data to sqrt(). Also, including … #include <math.h> … and compiling with … -lm … is essential. Here’s what I do: check argc, convert string to double using strtod(), verify the number is non-negative, then call sqrt(). This approach ensures the program won’t crash and handles bad inputs gracefully.
This is a fantastic breakdown of debugging a common and frustrating error! Your methodical approach to input validation is spot on and addresses the root causes of segmentation faults in such scenarios. It’s a prime example of defensive programming that every developer should adopt.
The emphasis on including <math.h> and compiling with -lm is also a critical reminder for anyone working with mathematical functions. Thanks for sharing this robust solution!
Keep up the great work, everyone, and here’s to fewer segfaults! 