String Handling Summary:

String is an Array ending in NULL - ‘\0’

string.h and stdlib.h; - string functions

ctype.h; - character functions

Initialize using array or pointer notation:

· char *s = "abc";

· char yourString[11] = "Do Be Do";

· char myString[] = "Do Be Do";

Copying strings:

· Not: s = “Hello”

· Instead, strcpy or strncpy or sprintf

Comparing strings:

· Not s1 == s2

· Instead strcmp or strncmp ; 0 = equal;

Length:

· strlen – up to first null

· printf: remember %s prints the string up to the null; watch nulls inside strings or missing null at end of string

Extract parts from string: sscanf

Convert string to number:

· atoi – returns an integer stopping at the first non digit

· strtod, strtol,strtoul – send both a pointer to the string and a pointer to a pointer to a string. It returns a pointer to the unconverted portion of first string.

Command line arguments: character array, with 0 as program path

Read String from Standard Input:

· getchar: get characters one at a time until equal EOF integer (waits for Enter)

· fgets: read one string from input, up to newline character, appending NULL

· scanf: remember “%19s” to not get to limit input, and you place the NULL

· scanf_s: safer, pass the length

Write string to Output:

· putchar to put a single character and

· puts to print one unformatted string

· printf – formatted output

List:

Library	Function	Purpose
string.h	char *strcpy( char *s1, const char *s2 )	Copies string s2 into array s1. The value of s1 is returned.
string.h	char *strncpy( char *s1, const char *s2, size_t n )	Copies at most n characters of string s2 into array s1. The value of s1 is returned.
string.h	char *strcat( char *s1, const char *s2 )	Appends string s2 to array s1. The first character of s2 overwrites the terminating null character of s1. The value of s1 is returned.
string.h	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
string.h	int strcmp( const char *s1, const char *s2 )	Compares the string s1 with the string s2. The function returns 0, less than 0 or greater than 0 if s1 is equal to, less than or greater than s2, respectively.
string.h	int strncmp( const char *s1, const char *s2, size_t n )	Compares up to n characters of the string s1 with the string s2. The function returns 0, less than 0 or greater
Stdio.h	int getchar( void )	Inputs the next character from the standard input and returns it as an integer.
Stdio.h	char *fgets( char *s, int n, FILE *stream)	Inputs characters from the specified stream into the array s until a newline or end-of-file character is encountered, or until n - 1 bytes are read. In this chapter, we specify the stream as stdin—the standard input stream, which is typically used to read characters from the keyboard. A terminating null character is appended to the array. Returns the string that was read into s.
Stdio.h	int putchar( int c )	Prints the character stored in c and returns it as an integer.
Stdio.h	int puts( const char *s )	Prints the string s followed by a newline character. Returns a non-zero integer if successful, or EOF if an error occurs.
Stdio.h	int sprintf( char *s, const char *format, ... )	Equivalent to printf, except the output is stored in the array s instead of printed on the screen. Returns the number of characters written to s, or EOF if an error occurs.
Stdio.h	int sscanf( char *s, const char *format, ... )	Equivalent to scanf, except the input is read from the array s rather than from the keyboard. Returns the number of items successfully read by the function, or EOF if an error occurs.
Stdlib.h	double atof( const char *nPtr )	Converts the string nPtr to double.
Stdlib.h	int atoi( const char *nPtr )	Converts the string nPtr to int.
Stdlib.h	long atol( const char *nPtr )	Converts the string nPtr to long int.
Stdlib.h	double strtod( const char *nPtr, char **endPtr )	Converts the string nPtr to double.
Stdlib.h	long strtol( const char *nPtr, char **endPtr, int base )	Converts the string nPtr to long.
Stdlib.h	unsigned long strtoul( const char *nPtr, char **endPtr, int base )	Converts the string nPtr to unsigned long.
Ctype.h	int isdigit( int c )	Returns a true value if c is a digit and 0 (false) otherwise.
Ctype.h	int isalpha( int c )	Returns a true value if c is a letter and 0 otherwise.
Ctype.h	int isalnum( int c )	Returns a true value if c is a digit or a letter and 0 otherwise.
Ctype.h	int isxdigit( int c )	Returns a true value if c is a hexadecimal digit character and 0
Ctype.h	int islower( int c )	Returns a true value if c is a lowercase letter and 0 otherwise.
Ctype.h	int isupper( int c )	Returns a true value if c is an uppercase letter and 0 otherwise.
Ctype.h	int tolower( int c )	If c is an uppercase letter, tolower returns c as a lowercase letter.
Ctype.h	int toupper( int c )	If c is a lowercase letter, toupper returns c as an uppercase letter.
Ctype.h	int isspace( int c )	Returns a true value if c is a white-space character—newline ('\n'), space (' '), form feed ('\f'), carriage return ('\r'), horizontal tab ('\t') or vertical tab ('\v')—and 0 otherwise

Prototypes from: Dietel, Paul and Harvey Dietel. C How to Program. New York: Pearson, 2013