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Using files to save data (C language)

2022-04-23 17:55:00 【Chshyz】

Save data to a local file

Environmental Science ：CentOS7
Common file operation functions and function tables are attached
file extension
.doc（Word file ）、.txt（ text file ）、.dat（ Data files ）、.c（C Language source file ）、.cpp（C++ Source program files ）、.for（FORTRAN Language source file ）、.pas（Pascal Language source file ）、.obj（ Target file ）、.exe（ Executable file ）、.ppt（ Electronic document slide ）、.bmp（ Graphic files ）、.jpg（ image file ）.

file type

  • Program files （ Executable ）
  • Data files （ASCII Files and binaries ）
    ①ASCII file ： text file , Each byte stores one character ASCII Code （ Character 、 Numerical type ）.
    ② Binary ： Output the data in the memory as it is to the disk for storage （ Numerical type ）.
    Example ： Input 10000
    ASCII Output to disk as （5 byte ）
    Output to disk in binary form （2 byte ）

The file pointer
Each used file opens up a corresponding file information area in memory to store file related information . There is a structure variable for this information （FILE） in .
example ：FILE * fp

Open and close files

  • Open data file （fopen）
    fopen ( file name , Use file mode );
    example ：
    FILE * fp; # Define a file that points to a variable fp
    fp = fopen (“a”, “r”); # take fopen The return value of the function is assigned to fp
  • Close file （fclose）
    fclose ( The file pointer )
    example ：fclose (fp);

PS：

Use Meaning
r read-only （ASCII file ）
w Just write （ASCII file ）
a Additional （ towards ASCII Add data at the end of the file ）
rb read-only （ Binary ）
wb Just write （ Binary ）
ab Additional （ Add data to the end of the binary file ）
r+ Reading and writing （ Open one ASCII File read and write ）
w+ Reading and writing （ Build a new one ASCII file ）
a+ Reading and writing （ASCII file ）
rb+ Reading and writing （ Binary ）
wb+ Reading and writing （ Binary ）
ab+ Reading and writing （ Binary ）

Example 1： The input is sent to disk 

#include <stdio.h>
#include <stdlib.h>
int main() {
    
    FILE * fp;
    char ch, filename[10];
    printf (" Please enter filename ：");
    scanf ("%s", filename);
    if ((fp = fopen (filename, "w")) == NULL) {
    
        printf (" Unable to open \n");
        exit (0);
        }
     ch = getchar();
     printf (" Please enter the content , With # End of no. ：");
     ch = getchar();
     while (ch != '#') {
    
        fputc (ch, fp);
        putchar (ch);
        ch = getchar ();
        }
      fclose (fp);
      putchar (10);
      return 0;
      }
      
[[email protected] c]# gcc -o fputc fputc.c
[[email protected] c]# ./fputc
 Please enter filename ：one
 Please enter the content , With # End of no. ：happy every days!#
happy every days!
[[email protected] c]# cat one
happy every days!

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https://yzsam.com/2022/04/202204230547413873.html

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