Here is a typical usage of fopen():

FILE *fp = fopen("numbers.txt", "r");
if (fp == NULL) {
fprintf(stderr, "cannot open file
");
exit(1);
}

Which of these indicate that a failure has happened?

Question

Here is a typical usage of fopen():

FILE *fp = fopen("numbers.txt", "r");
if (fp == NULL) {
    fprintf(stderr, "cannot open file
");
    exit(1);
}

Which of these indicate that a failure has happened?

BlackTom AI · Accepted Answer

fopen returns NULL on failure, and exit(1) causes the process to terminate with a non‑zero status that conventionally signals an error to the parent.

1) Relevant concepts
- fopen: on success returns a FILE*; on failure returns NULL (standard C behavior).
- exit(status): terminates the process and returns status to the parent; by convention a non‑zero status (commonly 1) indicates failure/error.
- stderr and fprintf simply print diagnostics and do not by themselves signal success/failure to the parent.

2) Step‑by‑step reasoning
- The code calls FILE *fp = fopen("numbers.txt", "r");
- Step 1: fopen either returns a valid FILE* (success) or NULL (failure).
- Step 2: The code checks if (fp == NULL). If true, it runs the body: fprintf(stderr, "cannot open file
"); exit(1);
- Step 3: exit(1) terminates the program and returns 1 to the parent process (shell or calling program).

3) Intermediate steps shown
- fopen -> result: either pointer != NULL (success) or pointer == NULL (failure).
- If pointer == NULL -> fprintf to stderr (message) -> exit(1) -> process exit status = 1.

4) Why the correct answer is correct
- The question asks which of these indicate that a failure has happened. In this code path, fopen returning NULL is the immediate indicator of the failure to open the file. Immediately after that check, exit(1) is invoked, causing the program to return a non‑zero exit code to the parent — another indicator that an error occurred. Both are therefore indicators of the same failure.

5) Why other options are incorrect
- "fopen returning a NULL pointer": correct as an indicator but incomplete because the program also signals failure via exit(1) in this code.
- "program returning exit code 1 to the parent": also a correct indicator but incomplete alone because the NULL return caused it.
- "none of these": incorrect because both mechanisms do indicate failure.

6) Conclusion
Both the NULL return from fopen and the program returning exit code 1 indicate that a failure occurred. This confirms the correct answer: both of these.

Here is a typical usage of fopen(): FILE *fp = fopen("numbers.txt", "r"); if (fp == NULL) { fprintf(stderr, "cannot open file\n"); exit(1); } Which of these indicate that a failure has happened?单项选择题

类似问题

Which is used to open “file.bin” for reading binary data in C?

In C, what does the fflush function do when used with a file stream?

What was the world's first widely adopted biodiversity policy?

The aim of the Paris Agreement is to ensure that the earth’s preindustrial temperature is not exceeded by more than º Celsius.

The IPCC's mission is to Blank ______.

Why have most international agreements for environmental protection been based on the honor system?

As was exhibited with the Montreal Protocol and the encouragement of reduced CFC production, trade can be an effective tool to compel compliance with international treaties.

The Stockholm Declaration and UNEP were the result of the Blank ______ first conference on the Human Environment in 1972.

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单