Details of gets, fgetc, fgets, Getc, getchar, putc, fputc, putchar, puts, fputs functions

1.gets( Read a string from the standard input device )：

The header file #include <stdio.h>
Defined function char * gets(char *s);
Function description gets() It is used to read characters from standard equipment and store them in parameters s The memory space referred to , Until a newline character appears or the end of the file is read ,
Then add NULL End as a string .
Return value gets() Return if successful s The pointer , return NULL It means there is an error .
Additional notes because gets() Unable to know string s Size , You must encounter a newline character or the end of the file to end the input , Therefore, it is easy to cause buffering
Security issues of overflow . It is recommended to use fgets() replace .
Example Reference resources fgets()

2.fgetc( Read a character from a file )：

The header file include<stdio.h>
Defined function nt fgetc(FILE * stream);
Function description fgetc() From parameter stream Read a character from the file referred to . If there is no data at the end of the file, it will return EOF.
Return value getc() The read characters will be returned , If returns EOF It means the end of the file .
Example

 #include <stdio.h> 
 int main(void) 
 {
     
	 FILE *fp=fopen("exist", "r"); //exist Represents the created file 
	 int c; 
	 while((c = fgetc(fp)) != EOF) 
		 printf("%c", c); 
	 fclose(fp); 
	 return 0;
 }

for example ：exist Change to 1.txt, hold 1.txt Write string in abc, The running result of the program is abc

3.fgets( Read a string from a file )：

The header file include<stdio.h>
Defined function har * fgets(char * s, int size, FILE * stream);
Function description fgets() Used to retrieve parameters from stream The characters read in the file referred to coexist in the parameter s The memory space referred to , Until a new line character appears 、
Read the end of the file or have read size-1 Up to characters , Finally, it will add NULL End as a string .
Return value gets() Return if successful s The pointer , return NULL It means there is an error .
Example

 #include <stdio.h> 
 int main(void) 
 {
     
	 char s[80]; 
	 fputs(fgets(s, 80, stdin), stdout); 
	 return 0;
 } 

For example, running a program
this is a apple // Input
this is a apple // Output （ adopt fgets To get the information entered from the keyboard ）

4.getc( Read a character from a file )：

The header file #include <stdio.h>
Defined function int getc(FILE * stream);
Function description getc() Used to retrieve parameters from stream Read a character from the file referred to . If there is no data at the end of the file, it will return EOF. although
getc() And fgetc() The same effect , but getc() Define... For macros , Non real function calls .
Return value getc() The read characters will be returned , If returns EOF It means the end of the file .
Example Reference resources fgetc().

5.getchar ( Read a character from the standard input device )：

The header file #include <stdio.h>
Defined function int getchar(void);
Function description getchar() Used to read a character from a standard input device , Then the character is changed from unsigned char convert to int After the return .
Return value getchar() The read characters will be returned , If returns EOF It means there is an error .
Additional notes getchar() Non real functions , It is getc(stdin) Macro definition .
Example

#include <stdio.h> 
int main(void) 
{
     
	FILE * fp; 
	int c, i; 
	for(i = 0; i < 5; i++) 
	{
     
	    c = getchar(); 
		putchar(c); 
	} 
	return 0;
} 

For example, running a program
abc // Input
abc // Output

6.putc( Write a specified character to the file )：

Defined function int putc(int c, FILE * stream);
Function description putc() Will set the parameters c To unsigned char Post write parameters stream In the specified file . although putc() And fputc()
The same effect , but putc() Define... For macros , Non real function calls .
Return value putc() It will return the characters successfully written , The parameter c. If returns EOF Then it means that the write failed .
Example Reference resources fputc().

7.fputc( Writes a specified character to the file stream )：

The header file #include <stdio.h>
Defined function int fputc(int c, FILE * stream);
Function description fputc Will set the parameters c To unsigned char Post write parameters stream In the specified file .
Return value fputc() It will return the characters successfully written , The parameter c. If returns EOF Then it means that the write failed .
Example

#include <stdio.h> 
int main(void) 
{
     
	FILE * fp; 
	char a[26] = "abcdefghijklmnopqrstuvwxyz"; 
    int i; 
	fp = fopen("noexist", "w"); 
	for(i = 0; i < 26; i++) 
		fputc(a[i], fp); 
	fclose(fp);
	return 0; 
}

for example ：noexist Change to 2.txt, You will find that the current folder generates a 2.txt file , And the content of the document is abcdefghijklmnopqrstuvwxyz

8.putchar( Writes the specified character to the standard output device )：

The header file #include <stdio.h>
Defined function int putchar (int c);
Function description putchar() Used to set the parameter c Characters are written to standard output devices .
Return value putchar() It will return the characters of successful output , The parameter c. If returns EOF It means that the output fails .
Additional notes putchar() Non real functions , It is putc(c, stdout) Macro definition .
Example Reference resources getchar().

9.puts( Used to output string to buffer )：

The header file #include <stdio.h>
Defined function int puts (char *string);
Function description putchar() Used to set the parameter c Characters are written to standard output devices .
Return value If this function outputs string to stream , Returns a nonzero value ; otherwise , return 0.
Additional notes putchar() Non real functions , It is putc(c, stdout) Macro definition .
Example

#include <stdio.h> 
int main(void) 
{
     
    char string[]="This is a test\n";
    puts(string);
	return 0;
} 

The result of running the program is This is a test

10.fputs( Writes a specified string to a file )：

The header file #include <stdio.h>
Defined function int fputs(const char *s, FILE *stream);
Function description fputs() Used to set the parameter s The indicated string is written to the parameter stream In the document referred to .
Return value If successful, the number of characters written out will be returned , return EOF It means there is an error .
Example Please refer to fgets().