char *readLine(int nr) {
   int ch, i=0;
   char *string;
   string = malloc(nr);
   while((ch = getchar()) != '\n') {
       if(i<nr && isdigit(ch)!=0) {
          string[i++]=ch;
       }
       else {
          string=NULL;
          return string;
       }
   }
   string[i]='
char *readLine(int nr) {
int ch, i=0;
char *string;
string = malloc(nr);
while((ch = getchar()) != '\n') {
if(i<nr && isdigit(ch)!=0) {
string[i++]=ch;
}
else {
string=NULL;
return string;
}
}
string[i]='\0';
return string;
} 
int main(void) {
int number;
printf("Enter number: ");
char *p=readLine(100);
if(p==NULL) {
printf("Invalid input!\n");
}
else {
number=atoi(p);
printf("Number as int is %d ", number);
}
free(p);
return 0;
}
';
   return string;
} 
int main(void) {
   int number;
   printf("Enter number: ");
   char *p=readLine(100);
   if(p==NULL) {
      printf("Invalid input!\n");
   }
   else {
      number=atoi(p);
      printf("Number as int is %d ", number);
   }
   free(p);
   return 0;
}

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
char *readLine(int nr) {
	int ch, i=0, q_entered = 0;
	char *string;
	string = malloc(nr);
	while((ch = getchar()) != '\n') {
		if(i<nr && !q_entered && isdigit(ch)!=0) {
			string[i++]=ch;
		} else if (i == 0 && ch == 'q') {
			string[i++] = ch;
			q_entered = 1;
		} else {
			free(string);
			return NULL;
		}
	}
	string[i]='
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
char *readLine(int nr) {
int ch, i=0, q_entered = 0;
char *string;
string = malloc(nr);
while((ch = getchar()) != '\n') {
if(i<nr && !q_entered && isdigit(ch)!=0) {
string[i++]=ch;
} else if (i == 0 && ch == 'q') {
string[i++] = ch;
q_entered = 1;
} else {
free(string);
return NULL;
}
}
string[i]='\0';
return string;
}
int main(void) {
int number;
printf("Enter number: ");
char *p=readLine(100);
if(p==NULL) {
printf("Invalid input!\n");
} else if (strcmp(p, "q") == 0) {
printf("Quitting\n");
} else {
number=atoi(p);
printf("Number as int is %d\n", number);
}
free(p);
return 0;
}
';
	return string;
}
int main(void) {
	int number;
	printf("Enter number: ");
	char *p=readLine(100);
	if(p==NULL) {
		printf("Invalid input!\n");
	} else if (strcmp(p, "q") == 0) {
		printf("Quitting\n");
	} else {
		number=atoi(p);
		printf("Number as int is %d\n", number);
	}
	free(p);
	return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#define MIN_INPUT_NUMBER 1
#define MAX_INPUT_NUMBER 20
void get_line_from_user( const char prompt[], char buffer[], int buffer_size );
int main( void )
{
    char line[200], *p;
    long num;
    //read exactly one line of input from the user
    get_line_from_user(
        "Please enter a number: ",
        line, sizeof line
    );
    //determine whether the user entered `"q"` as input
    if ( line[0] == 'q' && line[1] == '
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#define MIN_INPUT_NUMBER 1
#define MAX_INPUT_NUMBER 20
void get_line_from_user( const char prompt[], char buffer[], int buffer_size );
int main( void )
{
char line[200], *p;
long num;
//read exactly one line of input from the user
get_line_from_user(
"Please enter a number: ",
line, sizeof line
);
//determine whether the user entered `"q"` as input
if ( line[0] == 'q' && line[1] == '\0' )
{
printf( "Input is valid, user entered \"q\".\n" );
exit( EXIT_SUCCESS );
}
//attempt to convert input to a number
errno = 0;
num = strtol( line, &p, 10 );
//verify that at least one character was converted
if ( p == line )
{
printf( "Error: Unable to convert input to integer!\n" );
exit( EXIT_FAILURE );
}
//verify that input is not too small or too large to be
//representable as a `long int`
if ( errno == ERANGE )
{
printf( "Error: Input is outside the range of a long int!\n" );
exit( EXIT_FAILURE );
}
//verify that either all characters were converted or that all
//remaining characters are whitespace characters, so that input
//such as "242q42" gets rejected
for ( ; *p != '\0'; p++ )
{
if ( !isspace( (unsigned char)*p ) )
{
printf( "Error: Not all non-whitespace characters were converted!\n" );
exit( EXIT_FAILURE );
}
}
//verify that the converted integer is in the desired range
if ( num < MIN_INPUT_NUMBER || num > MAX_INPUT_NUMBER )
{
printf(
"Error: Input must be in the range %d to %d.\n",
MIN_INPUT_NUMBER, MAX_INPUT_NUMBER
);
exit( EXIT_FAILURE );
}
//everything went ok, so print the result
printf( "Input was valid! User entered %ld.\n", num );
return EXIT_SUCCESS;
}
//This function will read exactly one line of input from the
//user. It will remove the newline character, if it exists. If
//the line is too long to fit in the buffer, then the function
//will automatically reprompt the user for input. On failure,
//the function will never return, but will print an error
//message and call "exit" instead.
void get_line_from_user( const char prompt[], char buffer[], int buffer_size )
{
for (;;) //infinite loop, equivalent to while(1)
{
char *p;
//prompt user for input
fputs( prompt, stdout );
//attempt to read one line of input
if ( fgets( buffer, buffer_size, stdin ) == NULL )
{
printf( "Error reading from input!\n" );
exit( EXIT_FAILURE );
}
//attempt to find newline character
p = strchr( buffer, '\n' );
//make sure that entire line was read in (i.e. that
//the buffer was not too small to store the entire line)
if ( p == NULL )
{
int c;
//a missing newline character is ok if the next
//character is a newline character or if we have
//reached end-of-file (for example if the input is
//being piped from a file or if the user enters
//end-of-file in the terminal itself)
if ( (c=getchar()) != '\n' && !feof(stdin) )
{
if ( c == EOF )
{
printf( "Error reading from input!\n" );
exit( EXIT_FAILURE );
}
printf( "Input was too long to fit in buffer!\n" );
//discard remainder of line
do
{
c = getchar();
if ( c == EOF )
{
//this error message will be printed if either
//a stream error or an unexpected end-of-file
//is encountered
printf( "Error reading from input!\n" );
exit( EXIT_FAILURE );
}
} while ( c != '\n' );
//reprompt user for input by restarting loop
continue;
}
}
else
{
//remove newline character by overwriting it with
//null character
*p = '\0';
}
//input was ok, so break out of loop
break;
}
}
' )
    {
        printf( "Input is valid, user entered \"q\".\n" );
        exit( EXIT_SUCCESS );
    }
    //attempt to convert input to a number
    errno = 0;
    num = strtol( line, &p, 10 );
    //verify that at least one character was converted
    if ( p == line )
    {
        printf( "Error: Unable to convert input to integer!\n" );
        exit( EXIT_FAILURE );
    }
    //verify that input is not too small or too large to be
    //representable as a `long int`
    if ( errno == ERANGE )
    {
        printf( "Error: Input is outside the range of a long int!\n" );
        exit( EXIT_FAILURE );
    }
    //verify that either all characters were converted or that all
    //remaining characters are whitespace characters, so that input
    //such as "242q42" gets rejected
    for ( ; *p != '
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#define MIN_INPUT_NUMBER 1
#define MAX_INPUT_NUMBER 20
void get_line_from_user( const char prompt[], char buffer[], int buffer_size );
int main( void )
{
char line[200], *p;
long num;
//read exactly one line of input from the user
get_line_from_user(
"Please enter a number: ",
line, sizeof line
);
//determine whether the user entered `"q"` as input
if ( line[0] == 'q' && line[1] == '\0' )
{
printf( "Input is valid, user entered \"q\".\n" );
exit( EXIT_SUCCESS );
}
//attempt to convert input to a number
errno = 0;
num = strtol( line, &p, 10 );
//verify that at least one character was converted
if ( p == line )
{
printf( "Error: Unable to convert input to integer!\n" );
exit( EXIT_FAILURE );
}
//verify that input is not too small or too large to be
//representable as a `long int`
if ( errno == ERANGE )
{
printf( "Error: Input is outside the range of a long int!\n" );
exit( EXIT_FAILURE );
}
//verify that either all characters were converted or that all
//remaining characters are whitespace characters, so that input
//such as "242q42" gets rejected
for ( ; *p != '\0'; p++ )
{
if ( !isspace( (unsigned char)*p ) )
{
printf( "Error: Not all non-whitespace characters were converted!\n" );
exit( EXIT_FAILURE );
}
}
//verify that the converted integer is in the desired range
if ( num < MIN_INPUT_NUMBER || num > MAX_INPUT_NUMBER )
{
printf(
"Error: Input must be in the range %d to %d.\n",
MIN_INPUT_NUMBER, MAX_INPUT_NUMBER
);
exit( EXIT_FAILURE );
}
//everything went ok, so print the result
printf( "Input was valid! User entered %ld.\n", num );
return EXIT_SUCCESS;
}
//This function will read exactly one line of input from the
//user. It will remove the newline character, if it exists. If
//the line is too long to fit in the buffer, then the function
//will automatically reprompt the user for input. On failure,
//the function will never return, but will print an error
//message and call "exit" instead.
void get_line_from_user( const char prompt[], char buffer[], int buffer_size )
{
for (;;) //infinite loop, equivalent to while(1)
{
char *p;
//prompt user for input
fputs( prompt, stdout );
//attempt to read one line of input
if ( fgets( buffer, buffer_size, stdin ) == NULL )
{
printf( "Error reading from input!\n" );
exit( EXIT_FAILURE );
}
//attempt to find newline character
p = strchr( buffer, '\n' );
//make sure that entire line was read in (i.e. that
//the buffer was not too small to store the entire line)
if ( p == NULL )
{
int c;
//a missing newline character is ok if the next
//character is a newline character or if we have
//reached end-of-file (for example if the input is
//being piped from a file or if the user enters
//end-of-file in the terminal itself)
if ( (c=getchar()) != '\n' && !feof(stdin) )
{
if ( c == EOF )
{
printf( "Error reading from input!\n" );
exit( EXIT_FAILURE );
}
printf( "Input was too long to fit in buffer!\n" );
//discard remainder of line
do
{
c = getchar();
if ( c == EOF )
{
//this error message will be printed if either
//a stream error or an unexpected end-of-file
//is encountered
printf( "Error reading from input!\n" );
exit( EXIT_FAILURE );
}
} while ( c != '\n' );
//reprompt user for input by restarting loop
continue;
}
}
else
{
//remove newline character by overwriting it with
//null character
*p = '\0';
}
//input was ok, so break out of loop
break;
}
}
'; p++ )
    {
        if ( !isspace( (unsigned char)*p ) )
        {
            printf( "Error: Not all non-whitespace characters were converted!\n" );
            exit( EXIT_FAILURE );
        }
    }
    //verify that the converted integer is in the desired range
    if ( num < MIN_INPUT_NUMBER || num > MAX_INPUT_NUMBER )
    {
        printf(
            "Error: Input must be in the range %d to %d.\n",
            MIN_INPUT_NUMBER, MAX_INPUT_NUMBER
        );
        exit( EXIT_FAILURE );
    }
    //everything went ok, so print the result
    printf( "Input was valid! User entered %ld.\n", num );
    return EXIT_SUCCESS;
}
//This function will read exactly one line of input from the
//user. It will remove the newline character, if it exists. If
//the line is too long to fit in the buffer, then the function
//will automatically reprompt the user for input. On failure,
//the function will never return, but will print an error
//message and call "exit" instead.
void get_line_from_user( const char prompt[], char buffer[], int buffer_size )
{
    for (;;) //infinite loop, equivalent to while(1)
    {
        char *p;
        //prompt user for input
        fputs( prompt, stdout );
        //attempt to read one line of input
        if ( fgets( buffer, buffer_size, stdin ) == NULL )
        {
            printf( "Error reading from input!\n" );
            exit( EXIT_FAILURE );
        }
        //attempt to find newline character
        p = strchr( buffer, '\n' );
        //make sure that entire line was read in (i.e. that
        //the buffer was not too small to store the entire line)
        if ( p == NULL )
        {
            int c;
            //a missing newline character is ok if the next
            //character is a newline character or if we have
            //reached end-of-file (for example if the input is
            //being piped from a file or if the user enters
            //end-of-file in the terminal itself)
            if ( (c=getchar()) != '\n' && !feof(stdin) )
            {
                if ( c == EOF )
                {
                    printf( "Error reading from input!\n" );
                    exit( EXIT_FAILURE );
                }
                printf( "Input was too long to fit in buffer!\n" );
                //discard remainder of line
                do
                {
                    c = getchar();
                    if ( c == EOF )
                    {
                        //this error message will be printed if either
                        //a stream error or an unexpected end-of-file
                        //is encountered
                        printf( "Error reading from input!\n" );
                        exit( EXIT_FAILURE );
                    }
                } while ( c != '\n' );
                //reprompt user for input by restarting loop
                continue;
            }
        }
        else
        {
            //remove newline character by overwriting it with
            //null character
            *p = '
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#define MIN_INPUT_NUMBER 1
#define MAX_INPUT_NUMBER 20
void get_line_from_user( const char prompt[], char buffer[], int buffer_size );
int main( void )
{
char line[200], *p;
long num;
//read exactly one line of input from the user
get_line_from_user(
"Please enter a number: ",
line, sizeof line
);
//determine whether the user entered `"q"` as input
if ( line[0] == 'q' && line[1] == '\0' )
{
printf( "Input is valid, user entered \"q\".\n" );
exit( EXIT_SUCCESS );
}
//attempt to convert input to a number
errno = 0;
num = strtol( line, &p, 10 );
//verify that at least one character was converted
if ( p == line )
{
printf( "Error: Unable to convert input to integer!\n" );
exit( EXIT_FAILURE );
}
//verify that input is not too small or too large to be
//representable as a `long int`
if ( errno == ERANGE )
{
printf( "Error: Input is outside the range of a long int!\n" );
exit( EXIT_FAILURE );
}
//verify that either all characters were converted or that all
//remaining characters are whitespace characters, so that input
//such as "242q42" gets rejected
for ( ; *p != '\0'; p++ )
{
if ( !isspace( (unsigned char)*p ) )
{
printf( "Error: Not all non-whitespace characters were converted!\n" );
exit( EXIT_FAILURE );
}
}
//verify that the converted integer is in the desired range
if ( num < MIN_INPUT_NUMBER || num > MAX_INPUT_NUMBER )
{
printf(
"Error: Input must be in the range %d to %d.\n",
MIN_INPUT_NUMBER, MAX_INPUT_NUMBER
);
exit( EXIT_FAILURE );
}
//everything went ok, so print the result
printf( "Input was valid! User entered %ld.\n", num );
return EXIT_SUCCESS;
}
//This function will read exactly one line of input from the
//user. It will remove the newline character, if it exists. If
//the line is too long to fit in the buffer, then the function
//will automatically reprompt the user for input. On failure,
//the function will never return, but will print an error
//message and call "exit" instead.
void get_line_from_user( const char prompt[], char buffer[], int buffer_size )
{
for (;;) //infinite loop, equivalent to while(1)
{
char *p;
//prompt user for input
fputs( prompt, stdout );
//attempt to read one line of input
if ( fgets( buffer, buffer_size, stdin ) == NULL )
{
printf( "Error reading from input!\n" );
exit( EXIT_FAILURE );
}
//attempt to find newline character
p = strchr( buffer, '\n' );
//make sure that entire line was read in (i.e. that
//the buffer was not too small to store the entire line)
if ( p == NULL )
{
int c;
//a missing newline character is ok if the next
//character is a newline character or if we have
//reached end-of-file (for example if the input is
//being piped from a file or if the user enters
//end-of-file in the terminal itself)
if ( (c=getchar()) != '\n' && !feof(stdin) )
{
if ( c == EOF )
{
printf( "Error reading from input!\n" );
exit( EXIT_FAILURE );
}
printf( "Input was too long to fit in buffer!\n" );
//discard remainder of line
do
{
c = getchar();
if ( c == EOF )
{
//this error message will be printed if either
//a stream error or an unexpected end-of-file
//is encountered
printf( "Error reading from input!\n" );
exit( EXIT_FAILURE );
}
} while ( c != '\n' );
//reprompt user for input by restarting loop
continue;
}
}
else
{
//remove newline character by overwriting it with
//null character
*p = '\0';
}
//input was ok, so break out of loop
break;
}
}
';
        }
        //input was ok, so break out of loop
        break;
    }
}