What is the function of void *memset(s, c, n)?
Answer: B
Correct answer: places character c into first n characters of s, return s
Read the arguments in order: memset(s, c, n) fills the first n bytes of s with the byte c, and returns s. It is the usual way of zeroing a buffer, as memset(buf, 0, sizeof buf). Note that c is converted to unsigned char, so it sets bytes, not wider values.
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Functions whose names begin with “strn”
Answer: C
Correct answer: manipulates sequence of non – null characters.
The strn functions take an explicit count and process at most that many characters, so they do not depend on a terminating null being present. That is what makes them the safer choice with a fixed-size buffer - though strncpy in particular does not add a null of its own if the source fills the whole n.
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Which of the following is the right syntax to copy n characters from the object pointed to by s2 into the object pointed to by s1?
Answer: A
Correct answer: void *memcpy(void *s1,const void *s2,size_t n);
The destination comes first, as it does throughout the library - the same order as an assignment. The source is const, since it is only read, and the function returns void *, the destination pointer, so calls can be chained. The two regions must not overlap; memmove is the version that copes if they do.
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What does the function void *memmove(void *s1, const void *s2, size_t n); return?
Answer: A
Correct answer: returns the value of s1
memmove returns its destination pointer, s1 - as memcpy, strcpy and strcat all do. Returning the destination lets a call be used directly as an argument to another function. Its distinctive property is that it works correctly even when the two regions overlap, which memcpy does not guarantee.
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What is the return value of strxfrm()?
Answer: A
Correct answer: length of the transformed string, not including the terminating null-character
strxfrm transforms a string so that comparing two transformed strings with strcmp gives the same order as comparing the originals with strcoll. It returns the length of the transformed string, excluding the null - so a caller can size the buffer by calling it once with a length of 0.
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Is there any function declared as strstr()?
Answer: A
This function returns a pointer to the first occurrence in s1 of any of the entire sequence of characters specified in s2, or a null pointer if the sequence is not present in s1.
char *strstr(const char *s1, const char *s2)
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The C library function _________ breaks string s1 into a series of tokens using the delimiter s2.
Answer: A
Correct answer: char *strtok(char *s1,const char *s2);
strtok splits s1 into tokens separated by any of the characters in s2. The first call passes the string; every later call passes NULL to continue where it left off. Note that it modifies the string, writing a null over each delimiter, and keeps state between calls, which makes it unsuitable for reentrant or threaded code.
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The______function returns a pointer to the first character of a token.
Answer: D
Correct answer: strtok()
strtok() returns a pointer to the first character of the next token, or NULL when there are none left. It finds a token by skipping leading delimiters and then writing a null over the delimiter that ends it.
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Which of the following functions returns a pointer to the located string or a null pointer if string is not found.
Answer: B
Correct answer: strstr()
strstr(haystack, needle) searches for the first occurrence of one string inside another and returns a pointer to where it begins, or NULL if it is not there. strchr finds a single character rather than a string.
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Which of the given function is used to return a pointer to the located character?
Answer: D
Correct answer: strchr()
strchr() returns a pointer to the located character - the first occurrence of it in the string - or NULL. strrchr finds the last occurrence, memchr searches a fixed-length block rather than a string, and strxfrm transforms rather than searches.
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