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8.5 Standard Input/Output Library
Functions
• Functions in <stdio.h>
• Used to manipulate character and string data
Function prototype Function description
int getchar( void ); (^) Inputs the next character from the standard input and re-
turns it as an integer.
char *gets( char *s ); (^) Inputs characters from the standard input into the array s
until a newline or end-of-file character is encountered. A terminating null character is appended to the array. int putchar( int c ); (^) Prints the character stored in (^) c. int puts( const char *s ); (^) Prints the string s followed by a newline character. int sprintf( char *s, const char *format, ... ); Equivalent to^ printf, except the output is stored in the array s instead of printing it on the screen. int sscanf( char *s, const char *format, ... );
Equivalent to scanf, except the input is read from the array s instead of reading it from the keyboard.
fig08_13.c (Part 1 of 2)
1 /* Fig. 8.13: fig08_13.c 2 Using gets and putchar / 3 #include <stdio.h> 4 5 int main() 6 { 7 char sentence[ 80 ]; / create char array / 8 9 void reverse( const char * const sPtr ); / prototype / 10 11 printf( "Enter a line of text:\n" ); 12 13 / use gets to read line of text / 14 gets( sentence ); 15 16 printf( "\nThe line printed backwards is:\n" ); 17 reverse( sentence ); 18 19 return 0 ; / indicates successful termination / 20 21 } / end main */ 22
fig8_14.c
1 /* Fig. 8.14: fig08_14.c 2 Using getchar and puts / 3 #include <stdio.h> 4 5 int main() 6 { 7 char c; / variable to hold character input by user / 8 char sentence[ 80 ]; / create char array / 9 int i = 0 ; / initialize counter i / 10 11 / prompt user to enter line of text / 12 puts( "Enter a line of text:" ); 13 14 / use getchar to read each character / 15 while ( ( c = getchar() ) != '\n') { 16 sentence[ i++ ] = c; 17 } / end while / 18 19 sentence[ i ] = '\0'; 20 21 / use puts to display sentence / 22 puts( "\nThe line entered was:" ); 23 puts( sentence ); 24 25 return 0 ; / indicates successful termination / 26 27 } / end main */
Program Output
Enter a line of text:
This is a test.
The line entered was:
This is a test.
fig08_16.c
Program Output
1 /* Fig. 8.16: fig08_16.c 2 Using sscanf / 3 #include <stdio.h> 4 5 int main() 6 { 7 char s[] = "31298 87.375"; / initialize array s / 8 int x; / define x / 9 double y; / define y / 10 11 sscanf( s, "%d%lf", &x, &y ); 12 13 printf( "%s\n%s%6d\n%s%8.3f\n", 14 "The values stored in character array s are:", 15 "integer:", x, "double:", y ); 16 17 return 0 ; / indicates successful termination / 18 19 } / end main */
The values stored in character array s are:
integer: 31298
double: 87.
8.6 String Manipulation Functions of
the String Handling Library
• String handling library has functions to
– Manipulate string data
– Search strings
– Tokenize strings
– Determine string length
Function prototype Function description
char *strcpy( char
*s1, const char *s2 ) Copies string^ s2^ into array^ s1. The value of^ s1^ is returned.
char *strncpy( char
*s1, const char *s2,
size_t n )
Copies at most n characters of string s2 into array s1. The value of s is returned.
char *strcat( char
*s1, const char *s2 ) Appends string terminating null^ s2 character of^ to array^ s1. The first character ofs1. The value of s1 is returned.^ s2^ overwrites the
char *strncat( char
*s1, const char *s2,
size_t n )
Appends at most n characters of string s2 to array s1. The first character of s2 overwrites the terminating null character of s1. The value of s1 is returned.
fig08_19.c
1 /* Fig. 8.19: fig08_19.c 2 Using strcat and strncat / 3 #include <stdio.h> 4 #include <string.h> 5 6 int main() 7 { 8 char s1[ 20 ] = "Happy "; / initialize char array s1 / 9 char s2[] = "New Year "; / initialize char array s2 / 10 char s3[ 40 ] = ""; / initialize char array s3 / 11 12 printf( "s1 = %s\ns2 = %s\n", s1, s2 ); 13 14 / concatenate s2 to s1 / 15 printf( "strcat( s1, s2 ) = %s\n", strcat( s1, s2 ) ); 16 17 / concatenate first 6 characters of s1 to s3. Place '\0' 18 after last character / 19 printf( "strncat( s3, s1, 6 ) = %s\n", strncat( s3, s1, 6 ) ); 20 21 / concatenate s1 to s3 / 22 printf( "strcat( s3, s1 ) = %s\n", strcat( s3, s1 ) ); 23 24 return 0 ; / indicates successful termination / 25 26 } / end main */
Program Output
s1 = Happy
s2 = New Year
strcat( s1, s2 ) = Happy New Year
strncat( s3, s1, 6 ) = Happy
strcat( s3, s1 ) = Happy Happy New Year
fig08_21.c
1 /* Fig. 8.21: fig08_21.c 2 Using strcmp and strncmp */ 3 #include <stdio.h> 4 #include <string.h> 5 6 int main() 7 { 8 const char s1 = "Happy New Year"; / initialize char pointer */ 9 const char s2 = "Happy New Year"; / initialize char pointer */ 10 const char s3 = "Happy Holidays"; / initialize char pointer / 11 12 printf("%s%s\n%s%s\n%s%s\n\n%s%2d\n%s%2d\n%s%2d\n\n", 13 "s1 = ", s1, "s2 = ", s2, "s3 = ", s3, 14 "strcmp(s1, s2) = ", strcmp( s1, s2 ), 15 "strcmp(s1, s3) = ", strcmp( s1, s3 ), 16 "strcmp(s3, s1) = ", strcmp( s3, s1 ) ); 17 18 printf("%s%2d\n%s%2d\n%s%2d\n", 19 "strncmp(s1, s3, 6) = ", strncmp( s1, s3, 6 ), 20 "strncmp(s1, s3, 7) = ", strncmp( s1, s3, 7 ), 21 "strncmp(s3, s1, 7) = ", strncmp( s3, s1, 7 ) ); 22 23 return 0 ; / indicates successful termination / 24 25 } / end main */
Program Output
s1 = Happy New Year
s2 = Happy New Year
s3 = Happy Holidays
strcmp(s1, s2) = 0
strcmp(s1, s3) = 1
strcmp(s3, s1) = -
strncmp(s1, s3, 6) = 0
strncmp(s1, s3, 7) = 1
strncmp(s3, s1, 7) = -
fig08_23.c (Part 1 of 2)
1 /* Fig. 8.23: fig08_23.c 2 Using strchr */ 3 #include <stdio.h> 4 #include <string.h> 5 6 int main() 7 { 8 const char string = "This is a test"; / initialize char pointer / 9 char character1 = 'a'; / initialize character1 / 10 char character2 = 'z'; / initialize character2 / 11 12 / if character1 was found in string / 13 if ( strchr( string, character1 ) != NULL ) { 14 printf( "'%c' was found in "%s".\n", 15 character1, string ); 16 } / end if / 17 else { / if character1 was not found / 18 printf( "'%c' was not found in "%s".\n", 19 character1, string ); 20 } / end else */ 21
fig08_23.c (Part 2 of 2)
Program Output
22 /* if character2 was found in string / 23 if ( strchr( string, character2 ) != NULL ) { 24 printf( "'%c' was found in "%s".\n", 25 character2, string ); 26 } / end if / 27 else { / if character2 was not found / 28 printf( "'%c' was not found in "%s".\n", 29 character2, string ); 30 } / end else / 31 32 return 0 ; / indicates successful termination / 33 34 } / end main */
'a' was found in "This is a test".
'z' was not found in "This is a test".
