How to find substring from string

Question

How do I find a substring from the string path   user desktop abc post   using C C    I want to check if folder  abc  is present or not in that path   Path is character pointer char  ptr     user desktop abc post

User · Answer

In C   using namespace std   string my string   quot Hello world quot    string element to be found   quot Hello quot     if my string find element to be found   string  npos     std  cout lt  lt  quot Element Found quot  lt  lt std  endl

User · Answer

In C  use the strstr   standard library function   const char  str     user desktop abc post    const int exists   strstr str    abc       NULL    Take care to not accidentally find a too-short substring  this is what the starting and ending slashes are for

User · Answer

If you are utilizing arrays too much then you should include cstring h because it has too many functions including finding substrings

User · Answer

As user1511510 has identified  there s an unusual case when abc is at the end of the file name   We need to look for either  abc  or  abc followed by a string-terminator   0    A naive way to do this would be to check if either  abc  or  abc 0 are substrings    include  lt stdio h gt   include  lt string h gt   int main         const char  str     user desktop abc       const int exists   strstr str    abc       strstr str    abc 0        printf   d n  exists       return 0      but exists will be 1 even if abc is not followed by a null-terminator   This is because the string literal   abc 0  is equivalent to   abc    A better approach is to test if  abc is a substring  and then see if the character after this substring  indexed using the pointer returned by strstr    is either a   or a   0     include  lt stdio h gt   include  lt string h gt   int main         const char  str     user desktop abc    substr      const int exists    substr   strstr str    abc     amp  amp   substr 4       0     substr 4               printf   d n  exists       return 0      This should work in all cases

User · Answer

Example using std  string find method    include  lt iostream gt   include  lt string gt   int main         std  string str   There are two needles in this haystack with needles         std  string str2   needle         size t found   str find str2       if found  std  string  npos            std  cout  lt  lt   first  needle  found at     lt  lt  found  lt  lt    n              return 0      Result   first  needle  found at  14

User · Answer

Use std  string and find    std  string str     user desktop abc post    bool exists   str find   abc       std  string  npos

User · Answer

Use strstr const char  s   const char  t  and include lt string h gt   You can write your own function which behaves same as strstr and you can modify according to your requirement also  char   str str const char  s  const char  t    int i  j  k  for  i   0  s i       0   i       for  j i  k 0  t k     0   amp  amp  s j   t k   j    k     if  k  gt  0  amp  amp  t k       0   return   amp s i      return NULL

[c++] How to find substring from string?

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