Split string with delimiters in C

Question

How do I write a function to split and return an array for a string with delimiters in the C programming language   char  str    JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC   str split str

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Here is my two cents   int split  const char  txt  char delim  char    tokens        int  tklen   t  count   1      char   arr   p    char    txt       while   p      0   if   p      delim  count    1      t   tklen   calloc  count  sizeof  int        for  p    char    txt   p      0   p     p    delim    t       t          tokens   arr   malloc  count   sizeof  char          t   tklen      p    arr     calloc    t      1  sizeof  char          while   txt      0                 if   txt    delim                        p    arr     calloc    t      1  sizeof  char                  txt                      else  p      txt              free  tklen       return count      Usage   char   tokens  int count  i  const char  str    JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC    count   split  str        amp tokens   for  i   0  i  lt  count  i    printf    s n   tokens i        freeing tokens    for  i   0  i  lt  count  i    free  tokens i    free  tokens

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If you are willing to use an external library  I can t recommend bstrlib enough   It takes a little extra setup  but is easier to use in the long run   For example  split the string below  one first creates a bstring with the bfromcstr   call    A bstring is a wrapper around a char buffer   Next  split the string on commas  saving the result in a struct bstrList  which has fields qty and an array entry  which is an array of bstrings   bstrlib has many other functions to operate on bstrings  Easy as pie      include  bstrlib h   include  lt stdio h gt  int main       int i    char  tmp    Hello World sak     bstring bstr   bfromcstr tmp     struct bstrList  blist   bsplit bstr          printf  num  d n   blist- gt qty     for i 0 i lt blist- gt qty i          printf   d   s n   i  bstr2cstr blist- gt entry i

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include  lt string h gt   include  lt stdlib h gt   include  lt stdio h gt   include  lt errno h gt           splits str on delim and dynamically allocates an array of pointers         On error -1 is returned  check errno     On success size of array is returned  which may be 0 on an empty string     or 1 if no delim was found           You could rewrite this to return the char    array instead and upon NULL     know it s an allocation problem but I did the triple array here   Note that     upon the hitting two delim s in a row  foo  bar  the array would be         foo   NULL   bar             You need to define the semantics of a trailing delim Like  foo   is that a     2 count array or an array of one   I choose the two count with the second entry     set to NULL since it s valueless      Modifies str so make a copy if this is a problem     int split  char   str  char delim  char    array  int  length       char  p    char   res    int count 0    int k 0     p   str       Count occurance of delim in string   while   p strchr p delim      NULL          p   0     Null terminate the deliminator      p       Skip past our new null     count              allocate dynamic array   res   calloc  1  count   sizeof char        if   res   return -1     p   str    for  k 0  k lt count  k          if   p   res k    p      Copy start of string     p   strchr p  0          Look for next null     p       Start of next string         array   res     length   count     return 0     char str      JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC     int main       char   res    int k 0    int count  0    int rc     rc   split  str        amp res   amp count      if  rc         printf  Error   s errno   d  n   strerror errno   errno          printf  count   d n   count      for  k 0  k lt count  k           printf  str   s n   res k           free res      return 0

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You can use the strtok   function to split a string  and specify the delimiter to use   Note that strtok   will modify the string passed into it  If the original string is required elsewhere make a copy of it and pass the copy to strtok     EDIT   Example  note it does not handle consecutive delimiters   JAN   FEB MAR  for example     include  lt stdio h gt   include  lt stdlib h gt   include  lt string h gt   include  lt assert h gt   char   str split char  a str  const char a delim        char   result      0      size t count       0      char  tmp          a str      char  last comma   0      char delim 2       delim 0    a delim      delim 1    0          Count how many elements will be extracted         while   tmp                if  a delim     tmp                        count                last comma   tmp                    tmp                  Add space for trailing token         count    last comma  lt   a str   strlen a str  - 1           Add space for terminating null string so caller        knows where the list of returned strings ends         count         result   malloc sizeof char     count        if  result                size t idx    0          char  token   strtok a str  delim            while  token                        assert idx  lt  count                 result   idx      strdup token               token   strtok 0  delim                     assert idx    count - 1             result   idx    0             return result     int main         char months      JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC       char   tokens       printf  months   s  n n   months        tokens   str split months             if  tokens                int i          for  i   0    tokens   i   i                          printf  month   s  n     tokens   i                free   tokens   i                      printf   n            free tokens              return 0      Output       main exe months  JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC   month  JAN  month  FEB  month  MAR  month  APR  month  MAY  month  JUN  month  JUL  month  AUG  month  SEP  month  OCT  month  NOV  month  DEC

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Explode  amp  implode - initial string remains intact  dynamic memory allocation   include  lt stdio h gt   include  lt stdlib h gt   include  lt string h gt   include  lt errno h gt   typedef struct       uintptr t   ptr      int         size    token t   int explode char  str  int slen  const char  delimiter  token t   tokens        int i   0  c1   0  c2   0       for i   0  i  lt   slen  i                      if str i      delimiter                                c1                             if c1    0                    return -1              tokens    token t  calloc  c1   1   sizeof token t           tokens  c2   ptr    uintptr t str       i   0       while i  lt   slen                if  str i      delimiter      i    slen                                tokens  c2   size    int   uintptr t  amp  str i   -  uintptr t     tokens  c2   ptr                    if i  lt  slen                                        c2                           tokens  c2   ptr    uintptr t  amp  str i   1                                        i              return  c1   1      char  implode token t  tokens  int size  const char  delimiter        int     i  len   0      char     str       for i   0  i  lt  len  i                  len    tokens i  size   1             str    char  calloc len  sizeof char         len   0      for i   0  i  lt  size  i                  memcpy  void   amp str len    void  tokens i  ptr  tokens i  size           len    tokens i  size          str  len        delimiter             str len - 1      0        return str      Usage   int main int argc  char   argv        int         i  c      char         exp    JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC       token t      tokens      char         imp       printf   s n   exp        if  c   explode exp  strlen exp         amp tokens    gt  0                imp   implode tokens  c                printf   s n   imp            for i   0  i  lt  c  i                          printf     s   d n   tokens i  size   char  tokens i  ptr  tokens i  size                        free  void  tokens       free  void  imp       return 0

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I think the following solution is ideal    Doesn t destroy the source string Re-entrant - i e   you can safely call it from anywhere in one or more threads Portable Handles multiple separators correctly Fast and efficient   Explanation of the code    Define a structure token to store the address and lengths of the tokens Allocate enough memory for these in the worst case  which is when str is made up entirely of separators so there are strlen str    1 tokens  all of them empty strings Scan str recording the address and length of every token Use this to allocate the output array of the correct size  including an extra space for a NULL sentinel value Allocate  copy  and add the tokens using the start and length information - use memcpy as it s faster than strcpy and we know the lengths Free the token address and length array Return the array of tokens   typedef struct       const char  start      size t len    token   char   split const char  str  char sep        char   array      unsigned int start   0  stop  toks   0  t      token  tokens   malloc  strlen str    1    sizeof token        for  stop   0  str stop   stop              if  str stop     sep                tokens toks  start   str   start              tokens toks  len   stop - start              toks                start   stop   1                         Mop up the last token        tokens toks  start   str   start      tokens toks  len   stop - start      toks        array   malloc  toks   1    sizeof char         for  t   0  t  lt  toks  t                 Calloc makes it nul-terminated            char  token   calloc tokens t  len   1  1           memcpy token  tokens t  start  tokens t  len           array t    token               Add a sentinel        array t    NULL       free tokens       return array     Note malloc checking omitted for brevity   In general  I wouldn t return an array of char   pointers from a split function like this as it places a lot of responsibility on the caller to free them correctly  An interface I prefer is to allow the caller to pass a callback function and call this for every token  as I have described here  Split a String in C

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String tokenizer this code should put you in the right direction   int main void      char st     Where there is will  there is a way      char  ch    ch   strtok st          while  ch    NULL      printf   s n   ch     ch   strtok NULL               getch      return 0

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My approach is to scan the string and let the pointers point to every character after the deliminators and the first character   at the same time assign the appearances of deliminator in string to   0   First make a copy of original string since it s constant   then get the number of splits by scan it pass it to pointer parameter len  After that  point the first result pointer to the copy string pointer  then scan the copy string  once encounter a deliminator  assign it to   0  thus the previous result string is terminated  and point the next result string pointer to the next character pointer    char   split char  a str  const char a delim  int  len       char  s    char  malloc sizeof char    strlen a str        strcpy s  a str       char  tmp   a str      int count   0      while   tmp      0            if   tmp    a delim  count    1          tmp    1             len   count      char   results    char   malloc count   sizeof char         results 0    s      int i   1      while   s    0            if   s    a delim                s     0               s    1              results i      s                    else s    1            return results

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This optimized method create  or update an existing  array of pointers in  result and returns the number of elements in  count   Use  max  to indicate the maximum number of strings you expect  when you specify an existing array or any other reaseon   else set it to 0  To compare against a list of delimiters  define delim as a char  and replace the line   if  str i   delim      with the two following lines    char  c delim  while  c  amp  amp   c  str i   c     if   c      Enjoy   include  lt stdlib h gt   include  lt string h gt   char   split char  str  size t len  char delim  char    result  unsigned long  count  unsigned long max      size t i    char    result        there is at least one string returned    count 1      result   result        when the result array is specified  fill it during the first pass   if   result         result 0  str            scan the string for delimiter  up to specified length   for  i 0  i lt len    i            to compare against a list of delimiters         define delim as a string and replace         the next line             if  str i   delim                  with the two following lines             char  c delim  while  c  amp  amp   c  str i   c               if   c                      if  str i   delim              replace delimiter with zero       str i  0            when result array is specified  fill it during the first pass       if   result             result  count  str i 1                    increment count for each separator found           count             if max is specified  dont go further       if  max  amp  amp   count  max             break                           when result array is specified  we are done here   if   result        return  result            else allocate memory for result      and fill the result array                                                                                         result malloc   count  sizeof char       if    result        return NULL         result  result        add first string to result    result 0  str        if theres more strings   for  i 1  i lt  count    i            find next string     while  str    str        str          add next string to result      result i  str          return  result        Usage example    include  lt stdio h gt   int main int argc  char   argv      char  str  JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC     char   result malloc 6 sizeof char       char   result2 0    unsigned long count    unsigned long count2    unsigned long i     split strdup str  strlen str       amp result  amp count 6     split strdup str  strlen str       amp result2  amp count2 0      if  result    for  i 0  i lt count    i        printf   s n  result i           printf   n       if  result2    for  i 0  i lt count2    i        printf   s n   result2 i           return 0

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This function takes a char  string and splits it by the deliminator   There can be multiple deliminators in a row   Note that the function modifies the orignal string   You must make a copy of the original string first if you need the original to stay unaltered   This function doesn t use any cstring function calls so it might be a little faster than others   If you don t care about memory allocation  you can allocate sub strings at the top of the function with size strlen src str  2 and  like the c    version  mentioned  skip the bottom half of the function   If you do this  the function is reduced to O N   but the memory optimized way shown below is O 2N    The function   char   str split char  src str  const char deliminator  size t  amp num sub str       replace deliminator s with zeros and count how many     sub strings with length  gt   1 exist   num sub str   0    char  src str tmp   src str    bool found delim   true    while  src str tmp       if  src str tmp    deliminator          src str tmp   0        found delim   true            else if found delim     found first character of a new string       num sub str          found delim   false          sub str vec push back src str tmp     for c             src str tmp          printf  Start - found  d sub strings n   num sub str     if num sub str  lt   0       printf  str split   - no substrings were found n        return 0            if you want to use a c   vector and push onto it  the rest of this function     can be omitted  obviously modifying input parameters to take a vector  etc     char   sub strings    char    malloc   sizeof char     num sub str    1     const char  src str terminator   src str tmp    src str tmp   src str    bool found null   true    size t idx   0    while src str tmp  lt  src str terminator       if   src str tmp    found a NULL       found null   true      else if found null         sub strings idx      src str tmp          printf  sub string  d    s  n   idx-1  sub strings idx-1          found null   false            src str tmp          sub strings num sub str    NULL     return sub strings       How to use it     char months      JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC     char  str   strdup months     size t num sub str    char   sub strings   str split str       num sub str     char  endptr    if sub strings       for int i   0  sub strings i   i          printf    s  n   sub strings i          free sub strings     free str

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This is a string splitting function that can handle multi-character delimiters  Note that if the delimiter is longer than the string that is being split  then buffer and stringLengths will be set to  void    0  and numStrings will be set to 0   This algorithm has been tested  and works   Disclaimer  It has not been tested for non-ASCII strings  and it assumes that the caller gave valid parameters   void splitString const char  original  const char  delimiter  char      buffer  int   numStrings  int     stringLengths       const int lo   strlen original       const int ld   strlen delimiter       if ld  gt  lo            buffer    void   0           numStrings   0           stringLengths    void   0          return              numStrings   1       for int i   0 i  lt   lo - ld  i             if strncmp  amp original i   delimiter  ld     0                i     ld - 1                 numStrings                           stringLengths    int    malloc sizeof int     numStrings        int currentStringLength   0      int currentStringNumber   0      int delimiterTokenDecrementCounter   0      for int i   0 i  lt  lo i             if delimiterTokenDecrementCounter  gt  0               delimiterTokenDecrementCounter--            else if i  lt   lo - ld                if strncmp  amp original i   delimiter  ld     0                     stringLengths  currentStringNumber    currentStringLength                  currentStringNumber                    currentStringLength   0                  delimiterTokenDecrementCounter   ld - 1                else                   currentStringLength                            else               currentStringLength                       if i     lo - 1                  stringLengths  currentStringNumber    currentStringLength                        buffer    char     malloc sizeof char        numStrings        for int i   0 i  lt   numStrings i               buffer  i     char    malloc sizeof char       stringLengths  i    1               currentStringNumber   0      currentStringLength   0      delimiterTokenDecrementCounter   0      for int i   0 i  lt  lo i             if delimiterTokenDecrementCounter  gt  0               delimiterTokenDecrementCounter--            else if currentStringLength  gt     stringLengths  currentStringNumber                  buffer  currentStringNumber  currentStringLength    0              delimiterTokenDecrementCounter   ld - 1              currentStringLength   0              currentStringNumber              else                 buffer  currentStringNumber  currentStringLength     char original i               currentStringLength                        buffer currentStringNumber  currentStringLength    0      Sample code   int main        const char  string    STRING-1 DELIM string-2 DELIM sTrInG-3       char   buffer      int numStrings      int   stringLengths       splitString string    DELIM     amp buffer   amp numStrings   amp stringLengths        for int i   0 i  lt  numStrings i             printf  String   s n   buffer i              Libraries    include  lt stdlib h gt   include  lt string h gt   include  lt stdio h gt

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Method below will do all the job  memory allocation  counting the length  for you  More information and description can be found here - Implementation of Java String split   method to split C string    int split  const char  str  char c  char    arr        int count   1      int token len   1      int i   0      char  p      char  t       p   str      while   p      0                 if   p    c              count            p                arr    char    malloc sizeof char     count       if   arr    NULL          exit 1        p   str      while   p      0                 if   p    c                          arr  i     char   malloc  sizeof char    token len                if    arr  i     NULL                  exit 1                token len   0              i                      p            token len                arr  i     char   malloc  sizeof char    token len        if    arr  i     NULL          exit 1        i   0      p   str      t      arr  i        while   p      0                 if   p    c  amp  amp   p      0                          t    p              t                      else                        t     0               i                t      arr  i                      p               return count      How to use it   int main  int argc  char    argv        int i      char  s    Hello  this is a test module for the string splitting        int c   0      char   arr   NULL       c   split s        amp arr        printf  found  d tokens  n   c        for  i   0  i  lt  c  i            printf  string   d   s n   i  arr i         return 0

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In the above example  there would be a way to return an array of null terminated strings  like you want  in place in the string  It would not make it possible to pass a literal string though  as it would have to be modified by the function    include  lt stdlib h gt   include  lt stdio h gt   include  lt string h gt   char   str split  char  str  char delim  int  numSplits         char   ret      int retLen      char  c       if     str    NULL                delim      0                       Either of those will cause problems            ret   NULL          retLen   -1            else               retLen   0          c   str              Pre-calculate number of elements            do                       if    c    delim                                 retLen                               c              while    c      0              ret   malloc    retLen   1     sizeof   ret              ret retLen    NULL           c   str          retLen   1          ret 0    str           do                       if    c    delim                                 ret retLen       amp c 1                    c     0                              c              while    c      0                if   numSplits    NULL                  numSplits   retLen             return ret     int main  int argc  char  argv           const char  str    JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC        char  strCpy      char   split      int num      int i       strCpy   malloc  strlen  str     sizeof   strCpy          strcpy  strCpy  str         split   str split  strCpy        amp num         if   split    NULL                 puts   str split returned NULL               else               printf    i Results   n   num             for   i   0  i  lt  num  i                           puts  split i                          free  split        free  strCpy         return 0      There is probably a neater way to do it  but you get the idea

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My version   int split char  str  const char delimeter  char    args        int cnt   1      char  t   str       while   t    delimeter  t         char  t2   t      while    t2             if   t2    delimeter  amp  amp    t2   1     delimeter  amp  amp    t2   1     0  cnt           args    malloc sizeof char     cnt        for int i   0  i  lt  cnt  i              char  ts   t          while   t    delimeter  amp  amp   t    0  t             int len    t - ts   1             args  i    malloc sizeof char    len           memcpy   args  i   ts  sizeof char     len - 1              args  i  len - 1    0           while   t    delimeter  t               return cnt

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Try use this   char   strsplit char  str  const char  delim       char   res   NULL      char   part      int i   0       char  aux   strdup str        part   strdup strtok aux  delim         while part           res    char   realloc res   i   1    sizeof char               res   i    strdup part            part   strdup strtok NULL  delim            i               res    char   realloc res  i   sizeof char           res   i    NULL       return res

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Two issues surrounding this question are memory management and thread safety   As you can see from the numerous posts   this isn t an easy task to accomplish seamlessly in C   I desired a solution that is    Thread safe    strtok is not thread safe  Does not employ malloc or any of it s derivatives  to avoid memory management issues  Checks array bounds on the individual fields  to avoid segment faults on unknown data   Works with multi-byte field separators  utf-8  ignores extra fields in the input provides soft error routine for invalid field lengths   The solution I came up meets all of these criteria   It s probably a little more work to setup than some other solutions posted here  but I think that in practice  the extra work is worth  it in order to avoid the common pitfalls of other solutions    include  lt stdio h gt   include  lt string h gt   struct splitFieldType       char  field      int   maxLength      typedef struct splitFieldType splitField   int strsplit splitField  fields  int expected  const char  input  const char  fieldSeparator  void   softError  int fieldNumber int expected int actual          int i      int fieldSeparatorLen strlen fieldSeparator       const char  tNext   tLast input       for  i 0  i lt expected  amp  amp   tNext strstr tLast  fieldSeparator    NULL    i            int len tNext-tLast          if  len gt  fields i  maxLength                softError i fields i  maxLength-1 len               len fields i  maxLength-1                    fields i  field len  0          strncpy fields i  field tLast len           tLast tNext fieldSeparatorLen            if  i lt expected            if  strlen tLast  gt fields i  maxLength                softError i fields i  maxLength strlen tLast              else               strcpy fields i  field tLast                     return i 1        else           return i            void monthSplitSoftError int fieldNumber  int expected  int actual        fprintf stderr  monthSplit  input field   d is  d bytes  expected  d bytes n  fieldNumber 1 actual expected       int main       const char  fieldSeparator        const char  input  JAN FEB MAR APRI MAY JUN JUL AUG SEP OCT NOV DEC FOO BAR      struct monthFieldsType       char field1 4       char field2 4       char field3 4       char field4 4       char field5 4       char field6 4       char field7 4       char field8 4       char field9 4       char field10 4       char field11 4       char field12 4       monthFields     splitField inputFields 12           monthFields field1   sizeof monthFields field1         monthFields field2   sizeof monthFields field2         monthFields field3   sizeof monthFields field3         monthFields field4   sizeof monthFields field4         monthFields field5   sizeof monthFields field5         monthFields field6   sizeof monthFields field6         monthFields field7   sizeof monthFields field7         monthFields field8   sizeof monthFields field8         monthFields field9   sizeof monthFields field9         monthFields field10  sizeof monthFields field10         monthFields field11  sizeof monthFields field11         monthFields field12  sizeof monthFields field12           int expected sizeof inputFields  sizeof splitField      printf  input data   s n   input     printf  expecting  d fields n  expected      int ct strsplit inputFields  expected  input  fieldSeparator  monthSplitSoftError      if  ct  expected        printf  string split  d fields  expected  d n   ct expected          for  int i 0 i lt expected   i        printf  field  d   s n  i 1 inputFields i  field          printf   n      printf  Direct structure access  field 10   s   monthFields field10       Below is an example compile and output   Note that in my example  I purposefully spelled out  APRIL  so that you can see how the soft error works     gcc strsplitExample c  amp  amp    a out input data  JAN FEB MAR APRIL MAY JUN JUL AUG SEP OCT NOV DEC FOO BAR expecting 12 fields monthSplit  input field  4 is 5 bytes  expected 3 bytes field 1  JAN field 2  FEB field 3  MAR field 4  APR field 5  MAY field 6  JUN field 7  JUL field 8  AUG field 9  SEP field 10  OCT field 11  NOV field 12  DEC  Direct structure access  field 10  OCT   Enjoy

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I think strsep is still the best tool for this   while   token   strsep  amp str         my fn token     That is literally one line that splits a string   The extra parentheses are a stylistic element to indicate that we re intentionally testing the result of an assignment  not an equality operator      For that pattern to work  token and str both have type char    If you started with a string literal  then you d want to make a copy of it first      More general pattern  const char  my str literal    JAN FEB MAR   char  token   str   tofree   tofree   str   strdup my str literal       We own str s memory now  while   token   strsep  amp str         my fn token   free tofree     If two delimiters appear together in str  you ll get a token value that s the empty string  The value of str is modified in that each delimiter encountered is overwritten with a zero byte - another good reason to copy the string being parsed first   In a comment  someone suggested that strtok is better than strsep because strtok is more portable  Ubuntu and Mac OS X have strsep  it s safe to guess that other unixy systems do as well  Windows lacks strsep  but it has strbrk which enables this short and sweet strsep replacement   char  strsep char   stringp  const char  delim      if   stringp    NULL    return NULL      char  token start    stringp     stringp   strpbrk token start  delim     if   stringp          stringp     0         stringp           return token start      Here is a good explanation of strsep vs strtok  The pros and cons may be judged subjectively  however  I think it s a telling sign that strsep was designed as a replacement for strtok

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Below is my strtok   implementation from zString library   zstring strtok   differs from standard library s strtok   in the way it treats consecutive delimiters   Just have a look at the code below sure that you will get an idea about how it works  I tried to use as many comments as I could   char  zstring strtok char  str  const char  delim        static char  static str 0          var to store last address        int index 0  strlength 0           integers for indexes        int found   0                      check if delim is found            delimiter cannot be NULL       if no more char left  return NULL as well            if  delim  0     str    0  amp  amp  static str    0           return 0       if  str    0          str   static str          get length of string        while str strlength           strlength            find the first occurance of delim        for  index 0 index lt strlength index            if  str index   delim 0                 found 1              break                    if delim is not contained in str  return str        if   found            static str   0          return str                check for consecutive delimiters      if first char is delim  return delim            if  str 0   delim 0             static str    str   1           return  char   delim                terminate the string       this assignmetn requires char    so str has to       be char   rather than  char            str index      0           save the rest of the string        if   str   index   1   0          static str    str   index   1       else         static str   0           return str      Below is an example usage       Example Usage       char str      A B   C         printf  1  s n  zstring strtok s              printf  2  s n  zstring strtok NULL              printf  3  s n  zstring strtok NULL              printf  4  s n  zstring strtok NULL              printf  5  s n  zstring strtok NULL              printf  6  s n  zstring strtok NULL           Example Output       1 A       2 B       3         4         5 C       6  null    The library can be downloaded from Github https   github com fnoyanisi zString

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My code  tested     include  lt stdio h gt   include  lt stdlib h gt   include  lt string h gt   int dtmsplit char  str  const char  delim  char    array  int  length       int i 0    char  token    char   res    char     malloc 0   sizeof char            get the first token       token   strtok str  delim      while  token    NULL                 res    char     realloc res   i   1    sizeof char              res i    token          i          token   strtok NULL  delim            array   res      length   i    return 1     int main         int i      int c   0      char   arr   NULL       int count  0       char str 80     JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC       c   dtmsplit str        amp arr   amp count       printf  Found  d tokens  n   count        for  i   0  i  lt  count  i            printf  string   d   s n   i  arr i        return 0       Result   Found 12 tokens  string  0  JAN string  1  FEB string  2  MAR string  3  APR string  4  MAY string  5  JUN string  6  JUL string  7  AUG string  8  SEP string  9  OCT string  10  NOV string  11  DEC

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Here is another implementation that will operate safely to tokenize a string-literal matching the prototype requested in the question returning an allocated pointer-to-pointer to char  e g  char      The delimiter string can contain multiple characters  and the input string can contain any number of tokens  All allocations and reallocations are handled by malloc or realloc without POSIX strdup   The initial number of pointers allocated is controlled by the NPTRS constant and the only limitation is that it be greater than zero  The char    returned contains a sentinel NULL after the last token similar to  argv   and in the form usable by execv  execvp and execve   As with strtok   multiple sequential delimiters are treated as a single delimiter  so  JAN FEB MAR APR MAY   JUN JUL AUG SEP OCT NOV DEC  will be parsed as if only a single     separates  MAY JUN    The function below is commented in-line and a short main   was added splitting the months  The initial number of pointers allocated was set at 2 to force three reallocation during tokenizing the input string    include  lt stdio h gt   include  lt stdlib h gt   include  lt string h gt    define NPTRS 2        initial number of pointers to allocate  must be  gt  0         split src into tokens with sentinel NULL after last token     return allocated pointer-to-pointer with sentinel NULL on success     or NULL on failure to allocate initial block of pointers  The number    of allocated pointers are doubled each time reallocation required      char   strsplit  const char  src  const char  delim        int i   0  in   0  nptrs   NPTRS           index  in out flag  ptr count        char   dest   NULL                         ptr-to-ptr to allocate fill        const char  p   src   ep   p               pointer and end-pointer            allocate validate nptrs pointers for dest        if    dest   malloc  nptrs   sizeof  dest              perror   malloc-dest            return NULL             dest   NULL       set first pointer as sentinel NULL         for            loop continually until end of src reached            if    ep    strchr  delim   ep         if at nul-char or delimiter char                size t len   ep - p                get length of token                if  in  amp  amp  len                      in-word and chars in token                    if  i    nptrs - 1             used pointer    allocated - 1                            realloc dest to temporary pointer validate                        void  tmp   realloc  dest  2   nptrs   sizeof  dest                       if   tmp                            perror   realloc-dest                            break      don t exit  original dest still valid                                              dest   tmp                 assign reallocated block to dest                        nptrs    2                 increment allocated pointer count                                         allocate validate storage for token                    if    dest i    malloc  len   1                          perror   malloc-dest i                         break                                    memcpy  dest i   p  len        copy len chars to storage                    dest i    len    0             nul-terminate  advance index                    dest i    NULL                 set next pointer NULL                              if    ep                           if at end  break                    break              in   0                             set in-word flag 0  false                       else       normal word char                if   in                            if not in-word                    p   ep                         update start to end-pointer                in   1                             set in-word flag 1  true                       ep         advance to next character               return dest     int main  void         char  str    JAN FEB MAR APR MAY   JUN JUL AUG SEP OCT NOV DEC             tokens                               pointer to pointer to char         if   tokens   strsplit  str                split string into tokens            for  char   p   tokens   p  p          loop over filled pointers                puts   p               free   p           don t forget to free allocated strings                      free  tokens           and pointers              Example Use Output      bin splitinput JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC   Let me know if you have any further questions

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