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Kategori : file file-pointer modes opening read write c file
This C programming tutorial explains following concepts
- Open a c file and what are the opening modes
- What is a File pointer
- Close a c file
- Read and write character to a file
File Opening:
The File Pointer:
OR
FILE*fp; // it specifies the file pointer.
Fp=fopen(file,mode);
File opening Modes:
The fopen function returns the null pointer, if it fails to open the file (most common reason is file does not exist).
How to close a file in the c language?
File Closing:
Where fp is a file pointer associated to a file which is to be closed.
fclose () function returns 0 if the close operation is successfully completed.
fclose () function returns EOF if any error occurs.
How to read and write character to a file using C language?
putc(character ch , file_pointer);
- Before read or write operation, a file should be opened.
- All standard file handing function of C are declared in stdio. h header file
- When a file is opened a point of memory is reserved for file to read and write this memory is called memory buffer.
- When a file is read it is first stored in the memory buffer and then program reads the file from the memory buffer.
- When a file is written, then it is written in buffer, then its contents are transferred on the disk.
- The transfer of data from buffer to the disk is called flushing of buffer.
- The writing and reading through file through disk is time consuming, therefore time of reading and writing data to a file is reduced through buffer.
See code example: write data into a text file c++ program
- A pointer is like a variable whose content is the address of another memory cell (variable).
- Represents a pointer to the variable with which it is used.
- A file is not directly accessible in C.
- File are accessed through I\O buffers.
- A file pointer is a variable of FILE type defined in stdio.h
- FILE* represents a pointer to a variable of FILE type.
- The fopen( )function is used to open a file.
OR
FILE*fp; // it specifies the file pointer.
Fp=fopen(file,mode);
File opening Modes:
- �r� open text file for reading,each file must exists before reading.
- �w� open a text file for writing, if the file already exists then its contents are overwritten, if it does not exists, it will be created.
- �a� open a text file for append. Data is appended at the end of existing file. If the file does not exist, it will be created.
- �r+� open a file for both reading and writing. The file must already exists
- �w+� open a file for reading and writing, its contents are overwritten if the file does not exist, it is created.
- �a+� open a text file for both reading and appending. If the file does not exist, it is created for both reading and writing.
see example code: Append data into a text file c programming source code
The fopen function returns the null pointer, if it fails to open the file (most common reason is file does not exist).
How to close a file in the c language?
File Closing:
- An open must be close after completing the task.
- When a file is close then the buffer is flushed (data is transferred on the disk).
- If the file is not close than the data may be lost.
- The fclose () function is used to close a file.
- Syntax:
Where fp is a file pointer associated to a file which is to be closed.
fclose () function returns 0 if the close operation is successfully completed.
fclose () function returns EOF if any error occurs.
How to read and write character to a file using C language?
- Once a file has been opened depending on its opening mode then either a character can be read from a file or character can be written to a file using the following function
- Putc( ):
- The putc( ) function writes a single character to the file.
- The putc ( ) function returns the characters, if it successfully writes it.
- The putc ( ) function returns the EOF if an error occurs.
putc(character ch , file_pointer);
see example: copy data from one text file to another c source code
Character ch can be character, int, constant or a variable.
File pointer specifies variable of FILE type associated with the file in witch character is to be written.
Character ch can be character, int, constant or a variable.
File pointer specifies variable of FILE type associated with the file in witch character is to be written.
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