Using files to save data (C language)

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!