[C crazy handouts] (16) C language file operations, C language handouts operations
1. Basic concepts of Files
Stores datasets on external media. A dataset name is the file name.
File category:
1) user perspective: common files and Device Files
2) Storage content:
Ascii file (Text File ):
Storage Process: Find the corresponding ascii code value based on the text ----> convert to binary -->
Writing to file
Read process: Binary --> 10 hexadecimal --> Find the corresponding character --> display
Binary file:
Binary data access
File Operation Process:
1) import the header file stdio. h
2) define the file pointer
3) open the file
4) operation files
5) close the file
File Operation Principle
2. File pointer
FILE struct
FILE * fp; struct pointer
Purpose: store the first address of a file, pointing to a file
3. Open and Close a file
Open fopen (file name, operation method );
Fopen ("a.txt", "r ");
// A.txt is found in the products directory by default./Users/apple/Library/Developer/Xcode/DerivedData/C15-Integrated Project-cmassyrpkwjxularuygrjqhojbwj/Build/Products/Debug
Fopen ("/Users/apple/Desktop/a.txt", "r ");
Operation Method:
R w a B + t
Read/write append level-2 read/write text
W -- when writing a file, if the file does not exist, create
'Overwrite if it exists
R + w + wb + a +
Close the file:
Fclose (File pointer );
4. file operation functions
1) Reading and Writing of bytes-type data
Write:
Fputc ('characters', file pointer );
Char c = 'a ';
Fputc (c, fp );
Read:
Char ch = fgetc (fp );
2) Reading and Writing string data
Write:
Fputs (array name/pointer name, fp); // fputs (array name, stdout );
Read:
Fgets (array name/pointer name, length, fp );
The actual number of characters read by fgets is-1.
1) The end of \ n and the end of EOF
3) read and write data blocks
Write:
Fwrite (write variable address, data block size, number of blocks, fp );
Int a = 123;
Fwrite (& a, sizeof (int), 1, fp );
Struct Student stu1;
Fwrite (& stu1, sizeof (struct Student), 1, fp );
Read:
Struct Student s1;
Fread (variable address, data block size, number of blocks, fp)
Fread (& s1, sizeof (struct Student), 1, fp );
// Use s1 for output
4) formatted read and write
Write Data and read data in a certain format
Write:
Fprintf (File pointer, "formatted string", variable list );
Fprintf (fp, "% d, % c, % d #", 10, 'A', 20 );
10, a, 20 #10, a, 20 #10, a, 20 #
Read
Fscanf (fp, "% d, % c, % d #", & a, & ch, & B );
Fprintf (fp, "% d, % s, % d", 20, "abc", 30 );
Fscanf (fp, "% d, % s, % d", & a, str, & B );
Str = abc, 30
Changed:
Fprintf (fp, "% d, % d, % s", 20, 20, "abc ");
Fscanf (fp, "% d, % d, % s", & a, & B, str );
5. Random File Reading
Set the position of the file's header pointer
The default fp is the first address pointing to the file.
1) rewind (fp); // fp points to the first address
2) fseek (fp, offset distance, starting point );
Fseek (fp, 32L, SEEK_SET); // offset 32 bytes from the file header
6. File Detection Functions
Feof () is used to check whether the file ends
If the end is not 0
To end 1
Disadvantage: One more execution
7. Introduction to other header files in C Language
Math. h
Stdio. h
Stdlib. h
Time. h
String. h