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Terminal password example

/* Terminal password example */ #include <stdio.h> #include <termios.h> #define PASSMAX 8 int main(void) { struct termios defrsett, newrsett; char password[PASSMAX + 1]; tcgetattr(fileno(stdin), &defrsett); newrsett = defrsett; newrsett.c_lflag &= ~ECHO; printf("Enter password: "); if(tcsetattr(fileno(stdin), TCSAFLUSH, &newrsett) != 0) fprintf(stderr, "Did not set attributes\n"); else { fgets(password, PASSMAX, stdin); tcsetattr(fileno(stdin), TCSANOW, &defrsett); fprintf(stdout, "\nYou enterd %s", password); } return 0; }

Get string from stream. Reads characters from stream and stores them as a C string into str until (num-1) characters have been read or either a newline or the end-of-file is reached, whichever happens first. A newline character makes fgets stop reading, but it is considered a valid character by the function and included in the string copied to str. A terminating null character is automatically appended after the characters copied to str. Notice that fgets is quite different from gets: not only fgets accepts a stream argument, but also allows to specify the maximum size of str and includes in the string any ending newline character.

Get the file descriptor from an open stream. The fileno() function returns the number of the file descriptor for the file designated by stream. This number can be used in POSIX input/output calls anywhere the value returned by open() can be used. The following symbolic values in <unistd.h> define the file descriptors that are associated with the C language stdin, stdout, and stderr files when the application is started. Returns the file descriptor number associated with a specified z/OSĀ® XL C/C++ I/O stream. The argument stream points to a FILE structure controlling a z/OS XL C/C++ I/O stream.

Assignment operators are used to assign the value, variable and function to another variable. Assignment operators in C are some of the C Programming Operator, which are useful to assign the values to the declared variables. Let's discuss the various types of the assignment operators such as =, +=, -=, /=, *= and %=. The following table lists the assignment operators supported by the C language: Simple assignment operator. Assigns values from right side operands to left side operand. Add AND assignment operator. It adds the right operand to the left operand and assign the result to the left operand.

In C, the "main" function is treated the same as every function, it has a return type (and in some cases accepts inputs via parameters). The only difference is that the main function is "called" by the operating system when the user runs the program. Thus the main function is always the first code executed when a program starts. main() function is a user defined, body of the function is defined by the programmer or we can say main() is programmer/user implemented function, whose prototype is predefined in the compiler. Hence we can say that main() in c programming is user defined as well as predefined because it's prototype is predefined. main() is a system (compiler) declared function whose defined by the user, which is invoked automatically by the operating system when program is being executed.

#include is a way of including a standard or user-defined file in the program and is mostly written at the beginning of any C/C++ program. This directive is read by the preprocessor and orders it to insert the content of a user-defined or system header file into the following program. These files are mainly imported from an outside source into the current program. The process of importing such files that might be system-defined or user-defined is known as File Inclusion. This type of preprocessor directive tells the compiler to include a file in the source code program. Here are the two types of file that can be included using #include:

In the C Programming Language, the #define directive allows the definition of macros within your source code. These macro definitions allow constant values to be declared for use throughout your code. Macro definitions are not variables and cannot be changed by your program code like variables. You generally use this syntax when creating constants that represent numbers, strings or expressions.

Write formatted data to stream. Writes the C string pointed by format to the stream. If format includes format specifiers (subsequences beginning with %), the additional arguments following format are formatted and inserted in the resulting string replacing their respective specifiers. After the format parameter, the function expects at least as many additional arguments as specified by format.

The if-else statement is used to perform two operations for a single condition. The if-else statement is an extension to the if statement using which, we can perform two different operations, i.e., one is for the correctness of that condition, and the other is for the incorrectness of the condition. Here, we must notice that if and else block cannot be executed simiulteneously. Using if-else statement is always preferable since it always invokes an otherwise case with every if condition.

tcsetattr() only works in an environment where either a controlling terminal exists, or stdin and stderr refer to tty devices. Specifically, it does not work in a TSO environment. Changes the attributes associated with a terminal. New attributes are specified with a termios control structure. Programs should always issue a tcgetattr() first, modify the desired fields, and then issue a tcsetattr(). tcsetattr() should never be issued using a termios structure that was not obtained using tcgetattr(). tcsetattr() should use only a termios structure that was obtained by tcgetattr().

Writes the C string pointed by format to the standard output (stdout). If format includes format specifiers (subsequences beginning with %), the additional arguments following format are formatted and inserted in the resulting string replacing their respective specifiers. printf format string refers to a control parameter used by a class of functions in the input/output libraries of C programming language. The string is written in a simple template language: characters are usually copied literally into the function's output, but format specifiers, which start with a % character, indicate the location and method to translate a piece of data (such as a number) to characters. "printf" is the name of one of the main C output functions, and stands for "print formatted". printf format strings are complementary to scanf format strings, which provide formatted input (parsing). In both cases these provide simple functionality and fixed format compared to more sophisticated and flexible template engines or parsers,

Get string from stdin. Reads characters from the standard input (stdin) and stores them as a C string into str until a newline character or the end-of-file is reached. The newline character, if found, is not copied into str. A terminating null character is automatically appended after the characters copied to str. Notice that gets is quite different from fgets: not only gets uses stdin as source, but it does not include the ending newline character in the resulting string and does not allow to specify a maximum size for str (which can lead to buffer overflows).

The tcgetattr() function shall get the parameters associated with the terminal referred to by fildes and store them in the termios structure referenced by termios_p. The fildes argument is an open file descriptor associated with a terminal. The termios_p argument is a pointer to a termios structure. The tcgetattr() operation is allowed from any process. If the terminal device supports different input and output baud rates, the baud rates stored in the termios structure returned by tcgetattr() shall reflect the actual baud rates, even if they are equal. If differing baud rates are not supported, the rate returned as the output baud rate shall be the actual baud rate. If the terminal device does not support split baud rates, the input baud rate stored in the termios structure shall be the output rate (as one of the symbolic values).

C program search for an element in the linked list using recursion. Uses recursive function & search for an element in a Linked List. Linked List is an Ordered set of Data Elements, each

Program takes a number and checks whether a given number is Prime or not. Take number as Input & Check if the number is Divisible by any of the natural numbers starting from 2. If

Code find 2 Elements in the Array such that Difference between them is Largest. This C Program checks 2 elements in the array such that difference between them is largest and

Sum of upper triangular matrix is denoted with below image. In below image we need to find sum of matrix elements inside the red triangle. C program to read elements in a...

C Programming code finding the transpose of a martix in sparse form. Printing for testing sparse input. Calling function for evaluation of transpose. Printing the transposed matrix.