Files, tools and debugging
Real C programs read input, report errors and are tested under pressure.
What you will be able to do
- Check fopen, fread and fclose return values.
- Prefer fgets with a buffer size over gets.
- Use gdb, valgrind or sanitizers to reproduce failures.
In plain English
Use fopen with a mode, check every return value and close the file. fprintf writes formatted output; fgets reads a bounded line. A debugger and sanitizers are part of the language’s toolchain, not optional extras.
#include <stdio.h>
int main(void) {
FILE *file = fopen("notes.txt", "r");
if (file == NULL) {
perror("notes.txt");
return 1;
}
char line[256];
while (fgets(line, sizeof line, file) != NULL) {
printf("%s", line);
}
fclose(file);
return 0;
}Your turn
MediumRead a file safely
Open notes.txt for reading, print every line, and close the file. Handle a missing file.
C · starter
FILE *file = fopen("notes.txt", "r");Check your understanding before moving on.
Knowledge checkQuestion 1
Which function reads a bounded line from a file safely?
Select an answer to continue
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