The best example of scanf for strings i can make.

[mwiseca]

🏷️ Discussion Type

Product Feedback

Body

In all my projects i never use scanf for user input. I do sometimes try to make it work.
The example below works the best i came up with. It does white spaces and sends a error message when the user presses ctrl + d and sends the error message when the user just presses enter. I am sure there are better ways.

/Enter a selection from choices x to exit ch for choices.
//scb
//Enter the name of variable m for main.
//text
//Enter memory allocated to variable 2 or more.
//50
//Enter the name of the function to flush input buffer.
//flush
//Enter a error message. Enter valid text only will do.
//Enter valid text only.

while(scanf("%49[^\n]",text)!=1) {
flush();
printf("\nEnter valid text only.\n\n");
clearerr(stdin);
}

while(1) {
if(scanf("%49[^\n]",text)!=1) {
flush();
printf("\nEnter valid text only.\n\n");
clearerr(stdin);
continue;
}

//Enter a selection from choices x to exit ch for choices.

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[aiadam36]

Nice attempt! A few thoughts:

Your %49[^\n] scanset is the right instinct — it reads up to 49 chars and stops at newline, avoiding buffer overflows. The flush() + clearerr() combo to recover from EOF (Ctrl+D) is also correct.

That said, most experienced C devs avoid scanf for strings entirely and use fgets instead — it's simpler, safer, and handles all these edge cases more cleanly:

char text[50];

while (1) {
    if (!fgets(text, sizeof(text), stdin)) {
        clearerr(stdin);
        printf("\nEnter valid text only.\n\n");
        continue;
    }
    text[strcspn(text, "\n")] = '\0';
    if (text[0] == '\0') {
        printf("\nEnter valid text only.\n\n");
        continue;
    }
    break;
}

Key advantages over scanf:

• Handles whitespace naturally — no special scanset needed
• No flush function required; fgets always consumes the full line
• EOF is just a NULL check — no clearerr loop needed
• strcspn(text, "\n") strips the trailing newline cleanly in one line

Your scanf version isn't wrong, just more fragile. fgets is the idiomatic choice for interactive string input in C.

[mwiseca]

I was just showing a way to use scanf that i got to work the best. I actually use fgets in all my C projects even for
numbers.
Below is the way i use fgets. The if statement to clear the buffer must be one byte less with fgets with the getchar while loop to clear the buffer. If i just call the clear(); function without doing that i will have to press enter twice. The checkInput(); function contains clearerr(stdin); and a error message.

while(fgets(text, SIZE, stdin) == NULL) {
        checkInput();
    }
    text[strcspn(text, "\n")] = 0;
    if (strlen(text) >= MAX) {
        clear();
    }

[aiadam36]

Using scanf("%49[^\n]", text) with proper bounds is definitely better than bare scanf("%s", text), and I can see you're thinking through the edge cases (Ctrl+D, empty input, etc)

That said, here's the reality check: even with this pattern, scanf() is still fighting against its own design for safe string input. Here's why:

The core problem with scanf for strings

1. The flush() function — You're calling a custom function to clear leftover input, but scanf() doesn't actually give you great tools for this. You're probably using a loop like while(getchar() != '\n'); which works, but it's manual bookkeeping

2. Ctrl+D handling — scanf("%49[^\n]", text) will return 0 when EOF is hit, which you catch. Good! But this is fragile—behavior can differ across platforms

3. Mixing formatted and unformatted I/O — Every time you call clearerr(stdin) after scanf(), you're essentially patching around the fact that scanf() left the newline in the buffer

The simpler alternative

Instead, consider using fgets():

if (fgets(text, sizeof(text), stdin) != NULL) {
    text[strcspn(text, "\n")] = '\0';  // Remove newline
    // Process text
} else {
    // Handle EOF or error
}

Why this is cleaner:

• No custom flush function needed
• Ctrl+D handling is consistent
• Buffer size is baked in at the call site
• No clearerr() guessing games

Your approach is still solid for learning!

If this is for a learning project and you want to master scanf(), keep going—you're thinking about the right problems. But for production code or real-world projects, fgets() + manual parsing is the established pattern. Most C books now recommend it for exactly this reason.

Keep pushing on input validation though—that's a real skill

[mwiseca]

In the beginning of my post i wrote i never use scanf in any of my projects. I have some projects with
over 100 user inputs all fgets. I was just showing the best i can get scanf to work for strings.
I still wont use it for actual projects. Below is the first line of my post.
In all my projects i never use scanf for user input. I do sometimes try to make it work.
You are the second person to not notice that. That means i did not write the post properly.
In my last reply i showed how i use fgets in my projects to handle eof error and flush buffer.
Im sure yours will work as good or better than mine.
If you look at all the text you will see i did not write the code for the 2 scanfs i used a program that i made that
asks questions and than displays the code. Every thing else is a comment in case users accidentally
copy it to the program they are making.