Check substring exists in a string in C

Question

I m trying to check whether a string contains a substring in C like   char  sent    this is my sample example   char  word    sample   if     sentence contains word                        What is something to use instead of string  find in C

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My code to find out if substring is exist in string or not     input   first line -- gt  gt  string   2nd lin - gt  gt  gt  no  of queries for substring following n lines -- gt  gt  string to check if substring or not     include  lt stdio h gt  int len len1  int isSubstring char  s  char  sub int i int j             int ans  0           for  i lt len j lt len1 i   j                              if s i     sub j                                         ans  1                      break                                      if j    len1  amp  amp  ans   0                        return 1                    else if ans  1              return 0  return 0    int main        char s 100001       char sub 100001       scanf   s    amp s     Reading input from STDIN     int no      scanf   d   amp no       int i  j      i 0      j 0      int ans  0      len   strlen s       while no--                i 0          j 0          ans 0          scanf   s   amp sub           len1 strlen sub           int value          for i 0 i lt len i                              if s i   sub j                                         value   isSubstring s sub i j                       if value                                                printf  Yes n                            ans   1                          break                                                            if ans  0              printf  No n

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This code implements the logic of how search works  one of the ways  without using any ready-made function   public int findSubString char   original  char   searchString        int returnCode   0    0-not found  -1 -error in imput  1-found     int counter   0      int ctr   0      if  original Length  lt  1     original Length  lt searchString Length    searchString Length lt 1                returnCode   -1             while  ctr  lt    original Length - searchString Length   amp  amp  searchString Length  gt  0                if   original ctr      searchString 0                         counter   0              for  int count   ctr  count  lt   ctr   searchString Length   count                                  if  original count     searchString counter                                         counter                                      else                                       counter   0                      break                                              if  counter     searchString Length                                 returnCode   1                                  ctr              return returnCode

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You can try this one for both finding the presence of the substring and to extract and print it    include  lt stdio h gt   include  lt string h gt   int main void        char mainstring    The quick brown fox jumps over the lazy dog       char substring 20    ret      int i 0      puts  enter the sub string to find        fgets substring  sizeof substring   stdin       substring strlen substring -1    0       ret strstr mainstring substring       if strcmp  ret strstr mainstring substring   substring                 printf  substring is present t              printf  and the sub string is            for i 0 i lt strlen substring  i                      printf   c    ret i               puts   n        return 0

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Using C - No built in functions   string contains   does all the heavy lifting and returns 1 based index  Rest are driver and helper codes   Assign a pointer to the main string and the substring  increment substring pointer when matching  stop looping when substring pointer is equal to substring length   read line   - A little bonus code for reading the user input without predefining the size of input user should provide    include  lt stdio h gt   include  lt stdlib h gt   int string len char   string     int len   0    while  string    0        len        string          return len     int string contains char  string  char  substring     int start index   0    int string index 0  substring index 0    int substring len  string len substring     int s len   string len string     while substring index lt substring len  amp  amp  string index lt s len       if   string string index     substring substring index          substring index              string index        if substring index  substring len         return string index-substring len 1               return 0       define INPUT BUFFER 64 char  read line      int buffer len   INPUT BUFFER    char  input   malloc buffer len sizeof char      int c  count 0     while 1       c   getchar         if c  EOF  c    n          input count    0         return input       else        input count  c        count               if count  buffer len         buffer len  INPUT BUFFER        input   realloc input  buffer len sizeof char                  int main void      while 1       printf   nEnter the string          char  string   read line        printf  Enter the sub-string          char  substring   read line         int position   string contains string substring       if position          printf  Found at position   d n   position        else        printf  Not Found n                return 0

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if strstr sent  word     NULL                      Note that strstr returns a pointer to the start of the word in sent if the word word is found

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Try to use pointers      include  lt stdio h gt   include  lt string h gt   int main        char str      String1 subString1 Strinstrnd subStr ing1subString     char sub      subString      char  p1   p2   p3    int i 0 j 0 flag 0     p1   str    p2   sub     for i   0  i lt strlen str   i            if  p1     p2                    p3   p1            for j   0 j lt strlen sub  j                            if  p3     p2                              p3   p2                               else               break                        p2   sub            if j    strlen sub                            flag   1              printf   nSubstring found at index    d n  i                           p1           if flag  0             printf  Substring NOT found        return  0

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And here is how to report the position of the first character off the found substring   Replace this line in the above code   printf   s  substring   n      with   printf  substring  s was found at position  d  n   substring   int   substring - mainstring

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include  lt stdio h gt   include  lt string h gt   int findSubstr char  inpText  char  pattern   int main         printf  Hello  World  n        char  Text    This is my sample program       char  pattern    sample       int pos   findSubstr Text  pattern       if  pos  gt  -1            printf  Found the substring at position  d  n   pos             else         printf  No match found  n         return 0     int findSubstr char  inpText  char  pattern        int inplen   strlen inpText       while  inpText    NULL             char  remTxt   inpText          char  remPat   pattern           if  strlen remTxt   lt  strlen remPat                    printf   length issue remTxt  s  nremPath  s  n   remTxt  remPat                  return -1                     while   remTxt       remPat                  printf  remTxt  s  nremPath  s  n   remTxt  remPat               if   remPat      0                     printf   match found  n                    return inplen - strlen inpText 1                             if  remTxt    NULL                    return -1                                  remPat   pattern           inpText

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My own humble  case sensitive  solution   uint8 t strContains char  string  char  toFind        uint8 t slen   strlen string       uint8 t tFlen   strlen toFind       uint8 t found   0       if  slen  gt   tFlen                 for uint8 t s 0  t 0  s lt slen  s                          do                   if  string s     toFind t                                          if    found    tFlen   return 1                      s                        t                                      else   s -  found  found 0  t 0                    while found                     return 0            else return -1      Results  strContains  this is my sample example    th      1 strContains  this is my sample example    sample      1 strContains  this is my sample example    xam      1 strContains  this is my sample example    ple      1 strContains  this is my sample example    ssample      0 strContains  this is my sample example    samplee      0 strContains  this is my sample example          0 strContains  str    longer sentence      -1 strContains  ssssssample    sample      1 strContains  sample    sample      1   Tested on ATmega328P  avr8-gnu-toolchain-3 5 4 1709

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I believe that I have the simplest answer  You don t need the string h library in this program  nor the stdbool h library  Simply using pointers and pointer arithmetic will help you become a better C programmer   Simply return 0 for False  no substring found   or 1 for True  yes  a substring  sub  is found within the overall string  str      include  lt stdlib h gt   int is substr char  str  char  sub      int num matches   0    int sub size   0       If there are as many matches as there are characters in sub  then a substring exists    while   sub      0         sub size        sub           sub   sub - sub size      Reset pointer to original place    while   str      0         while   sub     str  amp  amp   sub      0           num matches          sub          str              if  num matches    sub size          return 1            num matches   0      Reset counter to 0 whenever a difference is found       str          return 0

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The same will be achived with this simpler code  Why use these   int main void         char mainstring    The quick brown fox jumps over the lazy dog       char substring 20       int i 0      puts  enter the sub stirng to find        fgets substring  sizeof substring   stdin       substring strlen substring -1    0       if  strstr mainstring substring                     printf  substring is present t              printf  and the sub string is           printf   s  substring   n       return 0      But the tricky part would be to report at which position in original string the substring starts

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Use strstr for this   http   www cplusplus com reference clibrary cstring strstr   So  you d write it like    char  sent    this is my sample example   char  word    sample    char  pch   strstr sent  word    if pch

[c] Check substring exists in a string in C

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