basename
#include <stdio.h>
#include <libgen.h>

int main (int argc, char *argv[])
{
    char *path = "/usr/include/libgen.h";
    char *p = basename(path);
    
    printf("Path     : %s\n",path);
    printf("basename : %s\n",p);

    return 0;
}
OUTPUT :
//  Path     : /usr/include/libgen.h
//  basename : libgen.h

index, rindex
#include <stdio.h>

int main (int argc, char *argv[])
{
     char *str = "first Test sTring";
     int ch = 'T';
     char *ptr;

     ptr = (char*)index(str,ch);
     printf("str : %s\n",str);
     printf("char to find : %c\n",ch);
     printf("first occurrence of %c is %s\n",ch,ptr);

     ptr = (char*)rindex(str,ch);
     printf("last occurrence of %c is %s\n",ch,ptr);
     return 0;
}
OUTPUT :
//  str : first Test sTring
//  char to find : T
//  first occurrence of T is Test sTring
//  last occurrence of T is Tring

strcasecmp
#include <stdio.h>
#include <string.h>

int main (int argc, char *argv[])
{
     char buff1[] = "first and last line";
     char buff2[] = "FIRST and LAST Line";

     int cmp = strcmp(buff1,buff2);

     puts("strcmp function :");
     if ( cmp == 0 )
         puts("buff1 and buff2 is equal");
     else if ( cmp > 0 )
         puts("buff1 is greater then buff2");
     else
         puts("buff1 is less then buff2");
     
     cmp = strcasecmp(buff1,buff2);

     puts("strcasecmp function :");
     if ( cmp == 0 )
         puts("buff1 and buff2 is equal");
     else if ( cmp > 0 )
         puts("buff1 is greater then buff2");
     else
         puts("buff1 is less then buff2");

     return 0;
}
OUTPUT :
//  strcmp function :
//  buff1 is greater then buff2
//  strcasecmp function :
//  buff1 and buff2 is equal

strcat
#include <stdio.h>
#include <string.h>

int main (int argc, char *argv[])
{
    char buff[256];
    char *s1  = "First string ";
    char s2[] = "Second string ";

    strcat(buff,s1);
    puts(buff);

    strcat(buff,s2);
    puts(buff);

    strcat(buff,"Third string");
    puts(buff);

    return 0;
}
OUTPUT :
//  First string
//  First string Second string
//  First stringSecond string Third string

strchr, strrchr
#include <stdio.h>
#include <string.h>

int main (int argc, char *argv[])
{
    char *str = "First test string";
    char *p1, *p2;
    int ch1 = 't';
    int ch2 = 'T';

    p1 = strchr(str,ch1);
    printf("First occurrence of %c:\n%s\n",ch1,p1);
    
    p2 = strrchr(str,ch1);
    printf("Last occurrence of %c:\n%s\n",ch1,p2);

    p1 = strchr(str,ch2);

    if ( !p1 )
        printf("Pattern %c not found",ch2);

    return 0;
}
OUTPUT :
//  First occurrence of t:
//  t test string
//  Last occurrence of t:
//  tring
//  Pattern T not found

strcmp, strncmp
#include <stdio.h>

#include <string.h>


int main (int argc, char *argv[])
{
    char buff1[] = "First String";
    char buff2[] = "First string";
    size_t cmp;

    puts(buff1);
    puts(buff2);
    puts(""); //  new line


    cmp = strcmp(buff1,buff2);

    if ( cmp == 0 )
        puts("first 5 char buff1 and buff2 are equal");
    else if ( cmp < 0 )
        puts("buff1 is less then string");
    else
        puts("buff1 is greater then string");

    cmp = strncmp (buff1,buff2,5);

    printf("cmp = %d\n",cmp);

    if ( cmp == 0 )
        puts("first 5 char buff1 and buff2 are equal");
    else if ( cmp < 0 )
        puts("buff1 is less then buff2");
    else
        puts("buff1 is greater then buff2");
        
    return 0;
}
//  First String

//  First string

//  

//  buff1 is greater then string

//  cmp = 0

//  first 5 char buff1 and buff2 are equal


strcpy
#include <stdio.h>
#include <string.h>

int main (int argc, char *argv[])
{
    char *str  = "First string, ";
    char ary[] = "Second string, ";
    char buff[255];

    strcpy(buff,str); //  constant string
    puts(buff);

    strcpy(buff,ary); //  array of characters
    puts(buff);
    
    strcpy(buff,"Third string\n");
    puts(buff);

    return 0;
}
OUTPUT :
//  First string, 
//  Second string, 
//  Third string

strcspn, strspn
#include <stdio.h>
#include <string.h>

int main (int argc, char *argv[])
{
    char *str = "First test string";
    char *reg1 = "u";
    char *reg2 = "uoag";
    size_t n;

    printf("str  : %s\n",str);
    printf("reg1 : %s\n",reg1);
    printf("reg2 : %s\n",reg2);

    n = strspn(str,reg1);
    printf("First occurrence of char from reg1 on\n\t\
            position %d\n",n);

    n = strcspn(str,reg2);
    printf("First occurrence of not char from reg2 on\n\t\
            position %d\n",n);

    return 0;
}
OUTPUT :

strdup, strndup
#include <stdio.h>
#include <string.h>

int main (int argc, char *argv[])
{
    char *str = "First Test String";
    char *p1, *p2;

    printf("original str : %s\n", str);

    //  p1 now is 0 terminated string
    p1 = strdup(str+11);
    printf("p1 : %s\n",p1);

    //  copy 11 characters from str
    //  start from 7th to p2.
    p2 = (char*)strndup(str+6,11);
    printf("p2 : %s\n",p2);

    return 0;
}
OUTPUT :
//  original str : First Test String
//  p1 : String
//  p2 : Test String

strlen
#include <stdio.h>
#include <string.h>

int main (int argc, char *argv[])
{
    int lenght, i;
    char buff[256], temp[3];
    char *s1  = "12345";
    char s2[] = "Two";  

    printf("Empty Buffer lenght = %d\n",strlen(buff));

    strcpy(buff,s1);
    printf("Buffer lenght = %d\n",strlen(buff));

    lenght = strlen(s2);
    for ( i = 0; i < lenght; i++ )
    {
        sprintf(temp,"%c",s2[i]);
        strcat(buff,temp);
        printf("Buffer lenght = %d\n",strlen(buff));
    }
    
    return 0;
}
OUTPUT :
//  Empty Buffer lenght = 1
//  Buffer lenght = 5
//  Buffer lenght = 6
//  Buffer lenght = 7
//  Buffer lenght = 8

strncasecmp
#include <stdio.h>
#include <string.h>

int main (int argc, char *argv[])
{
     char buff1[] = "first and last line";
     char buff2[] = "FIRST and LAST Line";

     int cmp = strncmp(buff1,buff2,5);

     puts("strcmp function :");
     if ( cmp == 0 )
         puts("buff1 and buff2 is equal");
     else if ( cmp > 0 )
         puts("buff1 is greater then buff2");
     else
         puts("buff1 is less then buff2");
     
     cmp = strncasecmp(buff1,buff2,5);

     puts("strcasecmp function :");
     if ( cmp == 0 )
         puts("buff1 and buff2 is equal");
     else if ( cmp > 0 )
         puts("buff1 is greater then buff2");
     else
         puts("buff1 is less then buff2");

     return 0;
}
OUTPUT :
//  strncmp function :
//  buff1 is greater then buff2
//  strncasecmp function :
//  buff1 and buff2 is equal

strncat
#include <stdio.h>
#include <string.h>

int main (int argc, char *argv[])
{
    char *p;
    int ch = 'A';
    char temp[3];


    p = (char*)malloc(26);

    for ( ; ch < 'K'; ch++ )
    {
        sprintf(temp,"%c",ch);
        strncat(p,temp,1);
        printf("%s\n",p);
    }

    return 0;
}
OUTPUT :
//  A
//  AB
//  ABC
//  ABCD
//  ABCDE
//  ABCDEF
//  ABCDEFG
//  ABCDEFGH
//  ABCDEFGHI
//  ABCDEFGHIJ

strncpy
#include <stdio.h>
#include <string.h>

int main (int argc, char *argv[])
{
    char s1[]  = "Long first string";
    char buff[256];
    size_t n = strlen(s1) - strlen(" string");

    strncpy(buff,s1,n);
    buff[n] = '\0';
    puts(buff);

    return 0;
}
OUTPUT :
//  Long first

strpbrk
#include <stdio.h>
#include <string.h>

int main (int argc, char *argv[])
{
    char *str = "First test string";
    char *pat = "uot";
    char *p;

    p = strpbrk(str,pat);

    printf("str     : %s\n",str);
    printf("pattern : %s\n",pat);
    printf("pointer fo first occurrence any\n\
            char into str from pat is : %s\n",
            p);

    return 0;
}
OUTPUT :
//  str     : First test string
//  pattern : uot
//  pointer fo first occurrence any
//          char into str from pat is : t test string

strsep
#include <stdio.h>
#include <string.h>

int main (int argc, char *argv[])
{
    char *str[] = {"first","second","third","forth"};
    char *pat = "third";
    char *p;

    p = (char*)strsep(str,pat);
    *p = '\0';

    puts(p);

    return 0;
}
OUTPUT :

strstr
#include <stdio.h>

int main (int argc, char *argv[])
{
     char *str = "First test string";
     char *pat = "test";
     char *p;

     p = (char*)strstr(str,pat);

     printf("str     : %s\n",str);
     printf("pattern : %s\n",pat);
     printf("first occurrence of entry pattern\n\
             into str is : %s\n",p);

     return 0;
}
OUTPUT :
//  str     : First test string
//  pattern : test
//  first occurrence of entry pattern
//               into str is : test string

strtok
#include <stdio.h>
#include <string.h>

int main (int argc, char *argv[])
{
    char *rec = "001:Linda Bain:F:42:programmer";
    char copy[256];
    char *p;
    int n = 0;
    char *field[] = {"      NAME : ",
        "       SEX : ",
        "       AGE : ",
        "occupation : "}; 

    //  const (*rec) will not works
    strcpy(copy,rec);

    //  first initialization of p
    p = strtok(copy,":");
    printf("        ID : %s\n",p);


    //  rest of tokens
    while ( (p = strtok(NULL,":")) != NULL )
    {
        printf("%s%s\n",field[n++],p);
    }

    return 0;
}
OUTPUT :
//  strtok destroys original string!!!
// 
//          ID : 001
//        NAME : Linda Bain
//         SEX : F
//         AGE : 42
//  occupation : programmer