Simple tutorial on programming in Linux (2) string-related operations

In fact, string operations are not part of programming in Linux. However, because programming in Linux is basically the programming of C language function libraries, it is essential to understand strings.

Strcasecmp

Function prototype: int strcasecmp (const char * S1, const char * S2)

Function: Compare ARGs [0] And ARGs [1], regardless of Case sensitivity.

Function return: If the return value is the same, 0 is returned. If the return value is S1 long, a positive number is returned. If the return value is S2 long, a negative number is returned.

Function parameters: S1 and S2 are the two strings to be compared.

Declaration file: String. h

Strcat

Function prototype: char * strcat (char * DEST, const char * SRC );

Function: connect the SRC string to the back of the Dest string. DeST requires sufficient space.

Function return: the first address of the Dest string.

Function parameter: DEST is the first address of the target string, and SRC is the first address of the source string.

Declaration file: String. h

Strchr

Function prototype: char * strchr (const char * STR, int ch );

Function: locate the location of the first ch character in the STR string.

Function return: the location of the CH character that appears for the first time.

Function parameter: STR is the first address of the string, and CH is the character to be searched.

Declaration file: String. h

Strcmp

Function prototype: int strcmp (const char * S1, const char * S2 );

Function: Compares string S1 and string S2. If the two are the same, 0 is returned. If S1 is different from S2, returns the subtract value of the first different S1 and S2 characters.

Function return: if the two are the same, 0 is returned. If S1 is different from S2, the first different S1 and S2 characters are returned, corresponding values after subtraction.

Function parameters: S1 and S2 are the two strings to be compared.

Declaration file: String. h

Strcpy

Function prototype: int strcpy (char * DEST, const char * SRC );

Function: copy the content of the SRC string to the position indicated by DeST.

Function return: the first address of the Dest string.

Function parameter: DEST is the first address of the target string, and SRC is the first address of the source string.

Declaration file: String. h

Strlen

Function prototype: size_t strlen (const char * Str );

Function: calculates the length of a specified string, excluding the ending character "\ 0 ".

Function return: the length of the STR string (excluding the number of characters including "\ 0 ).

Function parameter: String Of the length to be calculated.

Declaration file: String. h

Strstr

Function prototype: char * strstr (const char * STR, const char * substr );

Function: Search for the starting position of the first substring that matches the substr In the STR string.

Function return: Start position of the substring that matches the substr.

Function parameter: STR is the string to be scanned, and substr is the string to be searched.

Declaration file: String. h