The exit() Functions in C Programming Language

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The exit() Functions in C Programming Language

In case of any file input-output error or erroneous command line arguments, it is possible to terminate program execution. This can be done through the exit() function as shown in the following example: if( argc!= 3){printf("Invalid arguments\n");exit();} An integer may also be passed as a parameter to the exit() function. In UNIX, this value is stored in the environmental variable "$?", and should be in the range 0 - ...

The stdin, stdout and stderr FILE type Pointers

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The stdin, stdout and stderr FILE type Pointers

The stdin, stdout and stderr are names used to refer to the standard input device (keyboard) and standard output and error device (VDU). These are actually FILE type pointers, defined in the file stdio.h, and can be used with file input-output functions. For example, the following statement: fputc (c, stdout); writes the value of the char type variable c onto the VDU. The standard input, output and error files are not...

The NULL Return Value in C Language

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The NULL Return Value in C Language

In case fopen() is unsuccessfull in opening a file, it send s back a null(zero) value called NULL. NULL is defined in the file stdio.h. For example, the following statement. if((fp = fopen ("a.dat", "r")) == NULL) can be used to test whether the file a.dat has been opened successfully or not....

Closing Files in C Programming Language

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Closing Files in C Programming Language

Closing Files Each file is closed by one fclose() statement as shown in the following code: #include<stdio.h>main(){::fclose(ptr1);fclose(ptr2);} The above code is used to close files. fclose() statement is used to close files...

Reading from and writing to Files in C Language

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Reading from and writing to Files in C Language

In C, character input-output functions from files are simple extensions of the corresponding functions for input-ouput from/to the terminal. So, there are funcitons such as: fgetc()fputc() The only additional parameter of both functions is the appropriate file pointer, so that the file to be used for input-output is known. The following code performs the actual copying of contents of a.dat to b.dat: #include<stdio.h>main(){char...

Opening Files in C Language

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Opening Files in C Language

The C statements that would do this are: #include<stdio.h>main(){FILE *ptr1, *ptr2;ptr1 = fopen ("a.dat", "r");ptr2 = fopen ("b.dat", "w");--------} The function fopen() opens a file in the appropriate access mode. When a file is opened, certain information regarding that file automatically gets stored in different variables. These variables are collectively classified as the data type FILE. fopen() returns a pointer...

File Handling in C Programming Language

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File Handling in C Programming Language

The treatment of files in C is very simple, unlike that of other programming languages where there are special in-built and often rigid file structures and file-handling routines. C treats file input-output in much the same way as input-output from/ to the terminal, and provides file input-output functions, very similar to those for input-output from/to the terminal. The simplicity of the input-output in C lies in the fact...