How To Change String To An Int In C

Convert a String to Integer in C

Created: November-16, 2020 | Updated: March-30, 2021

atoi() Function to Convert a String to an Integer in C
strtol() Function to Convert a String to an Integer in C
strtoumax() Office for Convert Cord to an Integer in C

This article introduces different methods in a C programming language to convert a string into an integer. There are several methods for convert a string into an integer in C like atoi(), strtoumax() and strol().

`atoi()` Function to Convert a Cord to an Integer in C

The atoi() function converts a cord into an integer in the C programming language. The atoi() function neglects all white spaces at the beginning of the cord, converts the characters after the white spaces, so stops when it reaches the first non-number grapheme.

The atoi() function returns the integer representation of the string.

We need to include the <stdlib.h> header to use the atoi() office.

`atoi()` Syntax

              int atoi(const char *str);

*str is a pointer to a string to be converted to an integer.

`atoi()` Case Codes

              #include <stdio.h> #include <stdlib.h> #include <string.h>  int main (void)  {     int value;     char str[xx];     strcpy(str,"123");     value = atoi(str);     printf("String value = %s, Int value = %d\n", str, value);      return(0); }

Output:

              Cord value=123, Int value=123

`strtol()` Function to Catechumen a String to an Integer in C

The strtol() function converts a string into a long integer in the C programming linguistic communication. The strtol() role omits all white-spaces characters at the beginning of the cord, later it converts the subsequent characters as function of the number, then stops when it finds the showtime grapheme that isn't a number.

The strtol() function returns the long integer value representation of a string.

We need to include the <stdlib.h> header to utilise the atoi() function.

`strtol()` Syntax

              long int strtol(const char *string, char **laststr,int basenumber);

*string is a pointer to a string to be converted to a long integer.
**laststr is a pointer to bespeak where the conversion stops.
basenumber is the base with the range of [2, 36].

              #include <stdio.h> #include <stdlib.h> #include <string.h>  int main(void) {     char str[10];     char *ptr;     long value;     strcpy(str, " 123");     value = strtol(str, &ptr, 10);     printf("decimal %ld\due north", value);      return 0; }

Output:

              decimal 123

`strtoumax()` Office for Convert String to an Integer in C

The strtoumax() function interprets a string's content as in the form of an integral number of the specified base. It omits whatsoever whitespace grapheme until the showtime non-whitespace character. It so takes as many characters as possible to form a valid base integer number representation and converts them to an integer value.

strtoumax() returns the corresponding integer value of a string. This function returns 0 if the conversion is not successfully done.

`strtoumax()` Syntax

              uintmax_t strtoumax(const char* string, char** last, int basenumber);

*string is a arrow to a string to be converted to a long integer.
**last is a pointer to indicate where the conversion stops.
basenumber is the base with the range of [ii, 36].

`strtoumax()` Example

              #include <stdio.h> #include <stdlib.h> #include <string.h>   int main(void) {     char str[x];     char *ptr;     int value;     strcpy(str, " 123");     printf("The integer value:%d",strtoumax(str, &ptr,10));         render 0; }

Output:

              The long integer value: 123

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