C string operation

C string operation (conversion) Note: several case-insensitive comparison functions in the text use stricmp in the original article. Later I found that the STD library in Linux is not available and changed to the strcasecmp series.


Function Name: strcpy
Function: copy a string to another string.
Usage: char * strcpy (char * Destin, char * Source );
Program example:
# I nclude <stdio. h>
# I nclude <string. h>
Int main (void ){
Char string [10];
Char * str1 = "abcdefghi ";
Stpcpy (string, str1 );
Printf ("% s/n", string );
Return 0;
}
Function Name: strcat
Function: String concatenation Function
Usage: char * strcat (char * Destin, char * Source );
Program example:
# I nclude <string. h>
# I nclude <stdio. h>
Int main (void ){
Char destination [25];
Char * blank = "", * c = "C ++", * Borland = "Borland ";
Strcpy (destination, Borland );
Strcat (destination, blank );
Strcat (destination, C );
Printf ("% s/n", destination );
Return 0;
}
Function Name: strchr
Function: Find the first matching position of a given character in a string/
Usage: char * strchr (char * STR, char C );
Program example:
# I nclude <string. h> # I nclude <stdio. h>
Int main (void ){
Char string [15];
Char * PTR, c = 'R ';
Strcpy (string, "This is a string ");
PTR = strchr (string, C );
If (PTR)
Printf ("the character % C is at position: % d/N", C, PTR-string );
Else
Printf ("the character was not found/N ");
Return 0;
}
Function Name: strcmp
Function: String comparison
Usage: int strcmp (char * str1, char * str2 );
View ASIC code, str1> str2, return value> 0; two strings are equal, return 0 program example:
# I nclude <string. h>
# I nclude <stdio. h>
Int main (void ){
Char * buf1 = "AAA", * buf2 = "BBB", * buf3 = "CCC ";
Int PTR;
PTR = strcmp (buf2, buf1 );
If (PTR> 0)
Printf ("Buffer 2 is greater than buffer 1/N ");
Else
Printf ("Buffer 2 is less than buffer 1/N ");
PTR = strcmp (buf2, buf3 );
If (PTR> 0)
Printf ("Buffer 2 is greater than buffer 3/N ");
Else
Printf ("Buffer 2 is less than buffer 3/N ");
Return 0;
}
Function Name: strncmpi
Function: compares a part of a string with another string regardless of case.
Usage: int strncmpi (char * str1, char * str2, unsigned maxlen );
Program example:
# I nclude <string. h>
# I nclude <stdio. h>
Int main (void)
{
Char * buf1 = "BBB", * buf2 = "BBB ";
Int PTR;
PTR = strcmpi (buf2, buf1 );
If (PTR> 0)
Printf ("Buffer 2 is greater than buffer 1/N ");
If (PTR <0)
Printf ("Buffer 2 is less than buffer 1/N ");
If (PTR = 0)
Printf ("Buffer 2 equals buffer 1/N ");
Return 0;
}
Function Name: strcpy
Function: Copy strings
Usage: char * strcpy (char * str1, char * str2 );
Program example:
# I nclude <stdio. h>
# I nclude <string. h>
Int main (void)
{
Char string [10];
Char * str1 = "abcdefghi ";
Strcpy (string, str1 );
Printf ("% s/n", string );
Return 0;
}
Function Name: strcspns
Function: Search for the content segment of the first given character set in the string.
Usage: int strcspn (char * str1, char * str2 );
Program example:
# I nclude <stdio. h>
# I nclude <string. h>
# I nclude <alloc. h>
Int main (void ){
Char * string1 = "1234567890 ";
Char * string2 = "747dc8 ";
Int length;
Length = strcspn (string1, string2 );
Printf ("character where strings intersect is at position % d/N", length );
Return 0;
}
Function Name: strdup
Function: copy the string to the new position.
Usage: char * strdup (char * Str );
Program example:
# I nclude <stdio. h>
# I nclude <string. h>
# I nclude <alloc. h>
Int main (void)
{
Char * dup_str, * string = "ABCDE ";
Dup_str = strdup (string );
Printf ("% s/n", dup_str );
Free (dup_str );
Return 0;
}
Function Name:
Strcasecmp

Function: Compares two strings in upper and lower case insensitive mode.
Usage: int
Strcasecmp (char * str1, char * str2 );
Program example:
# I nclude <string. h>
# I nclude <stdio. h>
Int main (void)
{
Char * buf1 = "BBB", * buf2 = "BBB ";
Int PTR;
PTR =
Strcasecmp (buf2, buf1 );
If (PTR> 0)
Printf ("Buffer 2 is greater than buffer 1/N ");
If (PTR <0)
Printf ("Buffer 2 is less than buffer 1/N ");
If (PTR = 0)
Printf ("Buffer 2 equals buffer 1/N ");
Return 0;
}
Function Name: strerror
Function: returns a pointer to the error message string.
Usage: char * strerror (INT errnum );
Program example:
# I nclude <stdio. h>
# I nclude <errno. h>
Int main (void)
{
Char * buffer;
Buffer = strerror (errno );
Printf ("error: % s/n", buffer );
Return 0;
}
Function Name:
Strcasecmp
Function: compares a string with another string, regardless of case.
Usage: int
Strcasecmp (char * str1, char * str2 );
Program example:
# I nclude <string. h>
# I nclude <stdio. h>
Int main (void)
{
Char * buf1 = "BBB", * buf2 = "BBB ";
Int PTR;
PTR =
Strcasecmp (buf2, buf1 );
If (PTR> 0)
Printf ("Buffer 2 is greater than buffer 1/N ");
If (PTR <0)
Printf ("Buffer 2 is less than buffer 1/N ");
If (PTR = 0)
Printf ("Buffer 2 equals buffer 1/N ");
Return 0 ;}
Function Name: strncmp
Function: String comparison
Usage: int strncmp (char * str1, char * str2, int maxlen );
Program example:
# I nclude <string. h>
# I nclude <stdio. h>
Int main (void)
{
Char * buf1 = "aaabbb", * buf2 = "bbbccc", * buf3 = "CCC ";
Int PTR;
PTR = strncmp (buf2, buf1, 3 );
If (PTR> 0)
Printf ("Buffer 2 is greater than buffer 1/N ");
Else
Printf ("Buffer 2 is less than buffer 1/N ");
PTR = strncmp (buf2, buf3, 3 );

If (PTR> 0)
Printf ("Buffer 2 is greater than buffer 3/N ");
Else
Printf ("Buffer 2 is less than buffer 3/N ");

Return (0 );
}
Function Name:
Strncasecmp
Function: compares a part of a string with a part of another string, regardless of case.
Usage: int
Strncasecmp (char * str1, char * str2 );
Program example:
# I nclude <string. h>
# I nclude <stdio. h>
Int main (void)
{
Char * buf1 = "bbbccc", * buf2 = "bbbccc ";
Int PTR;
PTR =
Strncasecmp (buf2, buf1, 3 );
If (PTR> 0)
Printf ("Buffer 2 is greater than buffer 1/N ");
If (PTR <0)
Printf ("Buffer 2 is less than buffer 1/N ");
If (PTR = 0)
Printf ("Buffer 2 equals buffer 1/N ");
Return 0;
}
Function Name: strncpy
Function: Copy strings
Usage: char * strncpy (char * Destin, char * Source, int maxlen );
Program example:
# I nclude <stdio. h>
# I nclude <string. h>
Int main (void)
{
Char string [10];
Char * str1 = "abcdefghi ";
Strncpy (string, str1, 3 );
String [3] = '/0 ';
Printf ("% s/n", string );
Return 0;
}
Function Name: strnicmp
Function: Compares two strings case-insensitive.
Usage: int strnicmp (char * str1, char * str2, unsigned maxlen );
Program example:
# I nclude <string. h>
# I nclude <stdio. h>
Int main (void)
{
Char * buf1 = "bbbccc", * buf2 = "bbbccc ";
Int PTR;
PTR = strnicmp (buf2, buf1, 3 );
If (PTR> 0)
Printf ("Buffer 2 is greater than buffer 1/N ");
If (PTR <0)
Printf ("Buffer 2 is less than buffer 1/N ");
If (PTR = 0)
Printf ("Buffer 2 equals buffer 1/N ");
Return 0;
}
Function Name: strnset
Function: Set all characters in a string to a specified character.
Usage: char * strnset (char * STR, char CH, unsigned N );
Program example:
# I nclude <stdio. h>
# I nclude <string. h>
Int main (void)
{
Char * string = "abcdefghijklmnopqrstuvwxyz ";
Char letter = 'X ';
Printf ("string before strnset: % s/n", string );
Strnset (string, letter, 13 );
Printf ("string after strnset: % s/n", string );
Return 0;
}
Function Name: strpbrk
Function: searches for characters in a given character set in a string.
Usage: char * strpbrk (char * str1, char * str2 );
Program example:
# I nclude <stdio. h>
# I nclude <string. h>
Int main (void)
{
Char * string1 = "abcdefghijklmnopqrstuvwxyz ";
Char * string2 = "onm ";
Char * PTR;
PTR = strpbrk (string1, string2 );
If (PTR)
Printf ("strpbrk found first character: % C/N", * PTR );
Else
Printf ("strpbrk didn't find character in set/N ");
Return 0;
}
Function Name: strrchr
Function: Find the last occurrence of a specified character in the string.
Usage: char * strrchr (char * STR, char C );
Program example:
# I nclude <string. h>
# I nclude <stdio. h>
Int main (void)
{
Char string [15];
Char * PTR, c = 'R ';
Strcpy (string, "This is a string ");
PTR = strrchr (string, C );
If (PTR)
Printf ("the character % C is at position: % d/N", C, PTR-string );
Else
Printf ("the character was not found/N ");
Return 0;
}
Function Name: strrev
Power: String reversal
Usage: char * strrev (char * Str );
Program example:
# I nclude <string. h>
# I nclude <stdio. h>
Int main (void)
{
Char * Forward = "string ";
Printf ("before strrev (): % s/n", forward );
Strrev (forward );
Printf ("after strrev (): % s/n", forward );
Return 0;
}
Function Name: strset
Function: Set all characters in a string to a specified character.
Usage: char * strset (char * STR, char C );
Program example:
# I nclude <stdio. h>
# I nclude <string. h>
Int main (void ){
Char string [10] = "123456789 ";
Char symbol = 'C ';
Printf ("before strset (): % s/n", string );
Strset (string, symbol );
Printf ("after strset (): % s/n", string );
Return 0;
}
Function Name: strspns
Function: finds the first occurrence of a subset of a specified character set in a string.
Usage: int strspn (char * str1, char * str2 );
Program example:
# I nclude <stdio. h>
# I nclude <string. h>
# I nclude <alloc. h>
Int main (void)
{
Char * string1 = "1234567890 ";
Char * string2 = "123dc8 ";
Int length;
Length = strspns (string1, string2 );
Printf ("character where strings differ is at position % d/N", length );
Return 0;
}
Function Name: strstr
Function: Search for the first appearance of a specified string in the string.
Usage: char * strstr (char * str1, char * str2 );
Program example:
# I nclude <stdio. h>
# I nclude <string. h>
Int main (void)
{
Char * str1 = "Borland International", * str2 = "nation", * PTR;
PTR = strstr (str1, str2 );
Printf ("the substring is: % s/n", PTR );
Return 0 ;}
Function Name: strtodd
Function: converts a string to a double value.
Usage: Double strtodd (char * STR, char ** endptr );
Program example:
# I nclude <stdio. h>
# I nclude <stdlib. h>
Int main (void)
{
Char input [80], * endptr;
Double;
Printf ("enter a floating point number :");
Gets (input );
= Strtodd (input, & endptr );
Printf ("the string is % s the number is % lf/N", input ,);
Return 0;
}
Function Name: strtok
Function: searches for words separated by the delimiters specified in the second string.
Usage: char * strtok (char * str1, char * str2 );
Program example:
# I nclude <string. h>
# I nclude <stdio. h>
Int main (void)
{
Char input [16] = "ABC, D ";
Char * P;
/* Strtok places a null terminator in front of the token, if found */
P = strtok (input ,",");
If (P)
Printf ("% s/n", P );
/* A second call to strtok using a null
As the first parameter returns a pointer
To the character following the token
*/
P = strtok (null ,",");
If (P)
Printf ("% s/n", P );
Return 0;
}
Function Name: strtol
Function: converts a string to a long integer.
Usage: Long strtol (char * STR, char ** endptr, int base );
Program example:
# I nclude <stdlib. h>
# I nclude <stdio. h>
Int main (void)
{
Char * string = "87654321", * endptr;
Long lnumber;
/* Strtol converts string to long integer */
Lnumber = strtol (string, & endptr, 10 );
Printf ("string = % s long = % LD/N", String, lnumber );
Return 0;
}
Function Name: strupr
Function: converts lowercase letters in a string to uppercase letters.
Usage: char * strupr (char * Str );
Program example:
# I nclude <stdio. h>
# I nclude <string. h>
Int main (void)
{
Char * string = "abcdefghijklmnopqrstuvwxyz", * PTR;
/* Converts string to upper case characters */
PTR = strupr (string); printf ("% s/n", PTR );
Return 0;
}
Function Name: swab
Function: swap byte
Usage: void swab (char * From, char * To, int nbytes );
Program example:
# I nclude <stdlib. h>
# I nclude <stdio. h>
# I nclude <string. h>
Char source [15] = "rfna koblrna D"; char target [15];
Int main (void ){
Swab (source, target, strlen (source ));
Printf ("this is target: % s/n", target );
Return 0;
}

From: http://www.yuanma.org/data/2006/1029/article_1738.htm