C Library - <string.h> - GeeksforGeeks (2024)

C Library Function - difftime()

The difftime() is a C Library function that returns the difference in time, in seconds(i.e. ending time - starting time). It takes two parameters of type time_t and computes the time difference in seconds. The difftime() function is defined inside the &lt;time.h&gt; header file. Syntax The syntax of difftime() function is as follows: double difftim

wcstof function in C library

The wcstof() functions convert the initial portion of the wide-character string pointed to by str to a float point value. The str parameter points to a sequence of characters that can be interpreted as a numeric floating-point value. These functions stop reading the string at the first character that it cannot recognize as part of a number i.e. if

wprintf() and wscanf in C Library

If you are dealing with the wide characters then printf() and scanf() function cannot be used. There are different functions for input and output C wide string. wprintf() : The wprintf() function writes the wide string pointed to by format to stdout. The wide string format may contain format specifiers starting with % which are replaced by the valu

Difference between Header file and Library

Header Files: The files that tell the compiler how to call some functionality (without knowing how the functionality actually works) are called header files. They contain the function prototypes. They also contain Data types and constants used with the libraries. We use #include to use these header files in programs. These files end with .h extensi

ctype.h(&lt;cctype&gt;) library in C/C++ with Examples

As string.h header file contains inbuilt functions to handle Strings in C/C++, the ctype.h/&lt;cctype&gt; contains inbuilt functions to handle characters in C/C++ respectively. Characters are of two types: Printable Characters: The characters that are displayed on the terminal. Control Characters: The characters that are initiated to perform a spec

Check if two strings are same or not without using library functions

Given two strings S1 and S2, the task is to check whether they are the same or not without using string library functions. Examples: Input: S1 = ”GeeksForGeeks”, S2 = ”GeeksForGeeks”Output: TrueExplanation:S1 and S2 are the same strings Input: S1 = ”GeeksForGeeks”, S2 = ”GeeksforGeeks”Output: False Approach: Follow the steps below to solve the prob

free() Function in C Library With Examples

The free() function in C is used to free or deallocate the dynamically allocated memory and helps in reducing memory wastage. The C free() function cannot be used to free the statically allocated memory (e.g., local variables) or memory allocated on the stack. It can only be used to deallocate the heap memory previously allocated using malloc(), ca

C Library Function - putc()

In C, the putc() function is used to write a character passed as an argument to a given stream. It is a standard library function defined in the &lt;stdio.h&gt; header file. The function first converts the character to unsigned char, then writes it to the given stream at the position indicated by the file pointer, and finally increments the file po

C Library - exp() Function

In C programming language, the exp() function is a built-in function of &lt;math.h&gt; library which is used to calculate the value of e (Euler's Number = 2.71828) raised to the power x where x is any real number. Syntax: double exp(double x);Arguments: This function takes only one argument of type double.Return Type: This function returns the valu

C Library - math.h

The &lt;math.h&gt; header file in C contains the standard math library functions which can be utilized for various mathematical operations. All math.h library functions accept double type as an argument and return double as a result. It also contains some commonly used constants defined as macros. Syntax: #include &lt;math.h&gt;After including the

How to print range of basic data types without any library function and constant in C?

How to write C code to print range of basic data types like int, char, short int, unsigned int, unsigned char etc? It is assumed that signed numbers are stored in 2's complement form. We strongly recommend to minimize the browser and try this yourself first. Following are the steps to be followed for unsigned data types. 1) Find number of bytes for

How to add "graphics.h" C/C++ library to gcc compiler in Linux

While trying c graphic programming on Ubuntu, I figured out that graphic.h is not a standard C library and it is not supported by gcc compiler. So I am writing this article to explain the process.If you want to use graphics.h on Ubuntu platform you need to compile and install libgraph. It is the implementation of turbo c graphics API on Linux using

isgraph() C library function

The C library function isgraph() checks whether a character is a graphic character or not. Characters that have graphical representation are known are graphic characters. For example: ':' ';' '?' '@' etc. Syntax - #include &lt;ctype.h> int isgraph(int ch); Return Value - function returns nonzero if ch is any printable character other than a space,

How Do I Create a Library in C?

Libraries are a collection of code that can be used by other programs. They promote code reuse and modularity. In C, we can create our own libraries. In this article, we will learn how to create a library in C. Creating a Library in CIn C, there are multiple methods using which we can create a library.: Static LibraryDynamic LibraryIn this article,

How to Create a Static Library in C?

In C, we can create our own libraries that contains the code for the functions or macros that we may need very often. These libraries can be then used in our programs. In this article, we will learn how to create a custom static library and use it with GCC compiler. What is a Static Libraries in C?A static library is a collection of object files th

Print all possible combinations of the string by replacing '$' with any other digit from the string

Given a number as a string where some of the digits are replaced by a '$', the task is to generate all possible number by replacing the '$' with any of the digits from the given string.Examples: Input: str = "23$$" Output: 2322 2323 2332 2333Input: str = "$45" Output: 445 545 Approach: Find all the combinations of the string by replacing the charac

Lexicographically smallest string which is not a subsequence of given string

Given a string S, the task is to find the string which is lexicographically smallest and not a subsequence of the given string S. Examples: Input: S = "abcdefghijklmnopqrstuvwxyz"Output: aaExplanation:String "aa" is the lexicographically smallest string which is not present in the given string as a subsequence. Input: S = "aaaa"Output: aaabExplanat

How to find length of a string without string.h and loop in C?

Find the length of a string without using any loops and string.h in C. Your program is supposed to behave in following way: Enter a string: GeeksforGeeks (Say user enters GeeksforGeeks) Entered string is: GeeksforGeeks Length is: 13 You may assume that the length of entered string is always less than 100.The following is the solution. C/C++ Code #i

Print substring of a given string without using any string function and loop in C

Write a function mysubstr() in C that doesn't use any string function, doesn't use any loop, and prints substring of a string. The function should not modify contents of string and should not use a temporary char array or string. For example mysubstr("geeksforgeeks", 1, 3) should print "eek" i.e., the substring between indexes 1 and 3. One solution

What is the best way in C to convert a number to a string?

Solution: Use sprintf() function. #include&lt;stdio.h&gt; int main() { char result[50]; float num = 23.34; sprintf(result, &quot;%f&quot;, num); printf(&quot;\n The string for the num is %s&quot;, result); getchar(); } You can also write your own function using ASCII values of numbers.

C | String | Question 2

What is the output of following program? # include &lt;stdio.h&gt; int main() { char str1[] = &quot;GeeksQuiz&quot;; char str2[] = {'G', 'e', 'e', 'k', 's', 'Q', 'u', 'i', 'z'}; int n1 = sizeof(str1)/sizeof(str1[0]); int n2 = sizeof(str2)/sizeof(str2[0]); printf(&quot;n1 = %d, n2 = %d&quot;, n1, n2); return 0; } (A) n1 = 10, n2 = 9 (B) n1 = 10, n2

C | String | Question 3

What is the output of following program? #include&lt;stdio.h&gt; void swap(char *str1, char *str2) { char *temp = str1; str1 = str2; str2 = temp; } int main() { char *str1 = &quot;Geeks&quot;; char *str2 = &quot;Quiz&quot;; swap(str1, str2); printf(&quot;str1 is %s, str2 is %s&quot;, str1, str2); return 0; } (A) str1 is Quiz, str2 is Geeks (B) str1

C | String | Question 4

Predict the output? #include &lt;stdio.h&gt; int fun(char *str1) { char *str2 = str1; while(*++str1); return (str1-str2); } int main() { char *str = &quot;GeeksQuiz&quot;; printf(&quot;%d&quot;, fun(str)); return 0; } (A) 10 (B) 9 (C) 8 (D) Random Number Answer: (B) Explanation: The function fun() basically counts number of characters in input stri

C | String | Question 5

What does the following fragment of C-program print? char c[] = &quot;GATE2011&quot;; char *p =c; printf(&quot;%s&quot;, p + p[3] - p[1]) ; (A) GATE2011 (B) E2011 (C) 2011 (D) 011 Answer: (C) Explanation: See comments for explanation. char c[] = "GATE2011"; // p now has the base address string "GATE2011" char *p = c; // p[3] is 'E' and p[1] is 'A'.

C | String | Question 6

C/C++ Code #include int main() { char str[] = \"GeeksQuiz\"; printf(\"%s %s %s \", &str[5], &5[str], str+5); printf(\"%c %c %c \", *(str+6), str[6], 6[str]); return 0; } (A) Runtime Error (B) Compiler Error (C) uiz uiz uiz u u u (D) Quiz Quiz Quiz u u u Answer: (D)Explanation: The program has no error. All of the following expressions mean same thi

C | String | Question 7

In below program, what would you put in place of “?” to print “Quiz”? C/C++ Code #include int main() { char arr[] = \"GeeksQuiz\"; printf(\"%s\", ?); return 0; } (A)arr (B)(arr+5) (C)(arr+4) (D)Not possible Answer: (B)Explanation: Since %s is used, the printf statement will print everything starting from arr+5 until it finds ‘\\0’ Quiz of this Ques

C | String | Question 8

Output? int main() { char a[2][3][3] = {'g','e','e','k','s','q','u','i','z'}; printf(&quot;%s &quot;, **a); return 0; } (A) Compiler Error (B) geeksquiz followed by garbage characters (C) geeksquiz (D) Runtime Error Answer: (C) Explanation: We have created a 3D array that should have 2*3*3 (= 18) elements, but we are initializing only 9 of them. In

C | String | Question 9

Consider the following C program segment: char p[20]; char *s = &quot;string&quot;; int length = strlen(s); int i; for (i = 0; i &lt; length; i++) p[i] = s[length — i]; printf(&quot;%s&quot;, p); The output of the program is? (GATE CS 2004) (A) gnirts (B) gnirt (C) string (D) no output is printed Answer: (D) Explanation: Let us consider below line

C | String | Question 11

Predict the output of the following program: #include &lt;stdio.h&gt; int main() { char str[] = &quot;%d %c&quot;, arr[] = &quot;GeeksQuiz&quot;; printf(str, 0[arr], 2[arr + 3]); return 0; } (A) G Q (B) 71 81 (C) 71 Q (D) Compile-time error Answer: (C) Explanation: The statement printf(str, 0[arr], 2[arr + 3]); boils down to: printf("%d %c, 0["Geek

C | String | Question 12

Output of following program #include &lt;stdio.h&gt; int fun(char *p) { if (p == NULL || *p == '&#092;&#048;') return 0; int current = 1, i = 1; while (*(p+current)) { if (p[current] != p[current-1]) { p[i] = p[current]; i++; } current++; } *(p+i)='&#092;&#048;'; return i; } int main() { char str[] = &quot;geeksskeeg&quot;; fun(str); puts(str); ret