Linux C Basics

Linux C Basics

I. Basic data and functions

Int, Char, float, double

(1) format input and output

Scanf () // read the keyboard

Printf () // % d, % C, % s, % F

(2) Single Input/output character

Getchar ()

Putchar ()

Instance:

Int num;

Scanf ("% d", & num );

Printf ("num = % d", num );

Char;

A = getchar ();

Putchar ();

Ii. String

Strlen

Strcpy

Strcmp

Strcat

The difference between a string and a character array is that there is an empty character '\ 0' at the end of the string to end the string.

When reading a string using the scanf () Statement, spaces are not allowed in the input.

The gets () and puts () functions are used for the input and output of strings respectively.

Iii. Structure

Struct name {

...

};

Typedef definition type

Typedef int Myint;

Iv. File Operations

Fopen (if the opened file is in the current directory, the path can be omitted. Otherwise, the file name with a path is used. Note that escape characters '\' are used between directories at different levels '\\', you cannot use '\'. After opening the file, you must determine the return value and check whether the file is opened. Other operations can be continued only when the file is opened)
Fclose
Fflush clear stream

Fputc character output
Fgetc Character Input

Feof file ended

Fgets string Input
Fputs string output

Fread field input
Fwrite Field Output

Fprintf

Rewind File Location
Fseek (read/write location of a mobile file Stream)
Ftell (returns the current read/write location of the file stream)
Fgetpos, fsetpos, lseek

Ferror
Clearerr

Setbuf clears the stream

Instance:

    char filename[] = "/Users/kllmctrl/Desktop/HelloC/HelloC/test.txt";        FILE *fp;    if((fp=fopen(filename,"w"))==NULL)    {        printf("cannot open this file\n");        exit(0);    }    fclose(fp);