Linux C library functions Encyclopedia: string Processing functions

1. Atof (convert string to floating-point number)

Related functions

Atoi,atol,strtod,strtol,strtoul

Table header File

#include <stdlib.h>

Defining functions

Double atof (const char *nptr);

Function description

Atof () scans the parameter nptr string and skips the preceding space character until it encounters a number or sign to begin the conversion, and then ends the conversion without a number or at the end of the string, returning the result. The parameter nptr string can contain a positive sign, a decimal point, or E (e) to represent the exponent portion, such as 123.456 or 123e-2.

return value

Returns the number of floating-point types after conversion.

Additional Instructions

Atof () is the same as the result of using Strtod (nptr, (char**) NULL).

Example

/* Convert string A and string B to number after adding/*

#include <stdio.h> 
#include <stdlib.h> 
main () 
{ 
    char *a= " -100.23"; 
    Char *b= "200e-2"; 
    float C; 
    C=atof (a) +atof (b); 
    printf ("c=%.2f\n", c); 
}

2.atoi (convert string to Integer)

Related functions:

Atof,atol,atrtod,strtol,strtoul

Table header file:

#include <stdlib.h>

To define a function:

int atoi (const char *nptr);

Function Description:

Atoi () scans the parameter nptr string and skips the preceding space character until it encounters a number or sign to begin the conversion, and then ends the conversion without a number or at the end of the string, returning the result.

return value:

Returns the converted integer number.

Additional Instructions:

Atoi () with the use of Strtol (nptr, (char**) null,10);

Example:

/* Convert string A and string B to number after adding/*

#include <stdio.h> 
#include <stdlib.h> 
main () 
{ 
    char a[]= "; 
    " Char b[]= "256"; 
    int C; 
    C=atoi (a) +atoi (b); 
    printf ("c=%d\n", c); 
}