Read csv file in C

Question

I have a  csv file   lp imie nazwisko ulica numer kod miejscowosc telefon email data ur 1 Jan Kowalski ul  Nowa 1a 11-234 Budry 123-123-456 jan go xxx 1980 05 13 2 Jerzy Nowak ul  Konopnicka 13a 3 00-900 Lichowice  55 333-44-55 jer wu to 1990 03 23  and I need to read this in C  I have some code  but only for connection

User · Accepted Answer

Hopefully this would get you started

See it live on http://ideone.com/l23He (using stdin)

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

const char* getfield(char* line, int num)
{
    const char* tok;
    for (tok = strtok(line, ";");
            tok && *tok;
            tok = strtok(NULL, ";\n"))
    {
        if (!--num)
            return tok;
    }
    return NULL;
}

int main()
{
    FILE* stream = fopen("input", "r");

    char line[1024];
    while (fgets(line, 1024, stream))
    {
        char* tmp = strdup(line);
        printf("Field 3 would be %s\n", getfield(tmp, 3));
        // NOTE strtok clobbers tmp
        free(tmp);
    }
}

Output:

Field 3 would be nazwisko
Field 3 would be Kowalski
Field 3 would be Nowak

User · Answer

Thought I d share this code   It s fairly simple  but effective   It parses comma-separated files with parenthesis   You can easily modify it to suit your needs    include  lt stdio h gt   include  lt stdlib h gt   include  lt string h gt    int main int argc  char  argv          argv 1  path to csv file     argv 2  number of lines to skip     argv 3  length of longest value  in characters     FILE  pfinput    unsigned int nSkipLines  currentLine  lenLongestValue    char  pTempValHolder    int c    unsigned int vcpm    value character marker   int QuotationOnOff    0 - off  1 - on    nSkipLines   atoi argv 2      lenLongestValue   atoi argv 3       pTempValHolder    char  malloc lenLongestValue        if  pfinput   fopen argv 1   r            rewind pfinput        currentLine   1      vcpm   0      QuotationOnOff   0         currentLine  gt  nSkipLines condition skips ignores first argv 2  lines     while   c   fgetc pfinput      EOF               switch c                     case                  if  QuotationOnOff  amp  amp  currentLine  gt  nSkipLines                               pTempValHolder vcpm      0                 printf   s   pTempValHolder                 vcpm   0                            break            case   n               if currentLine  gt  nSkipLines                              pTempValHolder vcpm      0                 printf   s n  pTempValHolder                 vcpm   0                            currentLine                break            case                   if currentLine  gt  nSkipLines                              if  QuotationOnOff                    QuotationOnOff   1                  pTempValHolder vcpm    c                  vcpm                    else                   QuotationOnOff   0                  pTempValHolder vcpm    c                  vcpm                                              break            default              if currentLine  gt  nSkipLines                              pTempValHolder vcpm    c                vcpm                              break                      fclose pfinput        free pTempValHolder           return 0

User · Answer

With fscanf read the file until you encounter     or  n  then you can just skip it with fscang f   quot   c quot    int main         char str 128       int result      FILE  f   fopen  quot test txt quot    quot r quot                     do           result   fscanf f   quot  127    n  quot   str                    if result    0                        result   fscanf f   quot   c quot                      else                         whatever you want to do with your value             printf  quot  s n quot   str                            while result    EOF        return 0

User · Answer

A complete example which leaves the fields as NULL-terminated strings in the original input buffer and provides access to them via an array of char pointers  The CSV processor has been confirmed to work with fields enclosed in  double quotes   ignoring any delimiter chars within them    include  lt stdio h gt   include  lt stdlib h gt   include  lt string h gt      adjust BUFFER SIZE to suit longest line   define BUFFER SIZE 1024   1024  define NUM FIELDS 10  define MAXERRS 5  define RET OK 0  define RET FAIL 1  define FALSE 0  define TRUE 1     char  array will point to fields char  pFields NUM FIELDS      field offsets into pFields array   define LP          0  define IMIE        1  define NAZWISKo    2  define ULICA       3  define NUMER       4  define KOD         5  define MIEJSCOw    6  define TELEFON     7  define EMAIL       8  define DATA UR     9  long loadFile FILE  pFile  long  errcount   static int  loadValues char  line  long lineno   static char delim   long loadFile FILE  pFile  long  errcount        char sInputBuf  BUFFER SIZE       long lineno   0L       if pFile    NULL          return RET FAIL       while   feof pFile                 load line into static buffer         if fgets sInputBuf  BUFFER SIZE-1  pFile   NULL              break              skip first line  headers          if   lineno  1              continue              jump over empty lines         if strlen sInputBuf   0              continue             set pFields array pointers to null-terminated string fields in sInputBuf         if loadValues sInputBuf lineno   RET FAIL                errcount                 if  errcount  gt  MAXERRS                  break            else                      On return pFields array pointers point to loaded fields ready for load into DB or whatever                Fields can be accessed via pFields  e g              printf  lp  s  imie  s  data ur  s n   pFields LP   pFields IMIE   pFields DATA UR                        return lineno      static int  loadValues char  line  long lineno       if line    NULL          return RET FAIL          chop of last char of input if it is a CR or LF  e g Windows file loading in Unix env          can be removed if sure fgets has removed both CR and LF from end of line     if   line   strlen line -1       r       line   strlen line -1       n             line   strlen line -1      0       if   line   strlen line -1       r       line   strlen line -1       n             line   strlen line -1      0        char  cptr   line      int fld   0      int inquote   FALSE      char ch       pFields fld  cptr      while  ch  cptr       0   amp  amp  fld  lt  NUM FIELDS           if ch                       if   inquote                  pFields fld  cptr 1              else                    cptr     0                    zero out   and jump over it                           inquote     inquote            else if ch    delim  amp  amp    inquote                cptr     0                        end of field  null terminate it             pFields   fld  cptr 1                    cptr                 if fld  gt  NUM FIELDS-1           fprintf stderr   Expected field count   d  exceeded on line  ld n   NUM FIELDS  lineno           return RET FAIL        else if  fld  lt  NUM FIELDS-1           fprintf stderr   Expected field count   d  not reached on line  ld n   NUM FIELDS  lineno           return RET FAIL                return RET OK     int main int argc  char   argv       FILE  fp     long errcount   0L     long lines   0L      if argc  3          printf  Usage   s csvfilepath delimiter n   basename argv 0            return  RET FAIL              if  delim argv 2  0      0           fprintf stderr  delimiter must be specified n           return  RET FAIL           fp   fopen argv 1     r       if fp    NULL          fprintf stderr  Error opening file   d n  errno         return RET FAIL           lines loadFile fp  amp errcount      fclose fp      printf  Processed  ld lines  encountered  ld error s  n   lines  errcount      if errcount gt 0          return RET FAIL       return RET OK

User · Answer

The following code is in plain c language and handles blank spaces  It only allocates memory once  so one free   is needed  for each processed line   http   ideone com mSCgPM     Tiny CSV Reader       Copyright  C  2015  Deligiannidis Konstantinos  This program is free software  you can redistribute it and or modify it under the terms of the GNU General Public License as published by the Free Software Foundation  either version 3 of the License  or  at your option  any later version   This program is distributed in the hope that it will be useful  but WITHOUT ANY WARRANTY  without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE   See the GNU General Public License for more details   You should have received a copy of the GNU General Public License along with this program   If not  see  lt http   w   content-available-to-author-only   u org licenses  gt          include  lt stdio h gt   include  lt string h gt   include  lt stdlib h gt       For more that 100 columns or lines  when delimiter    n   minor modifications are needed     int getcols  const char   const line  const char   const delim  char    out storage      const char  start ptr   end ptr   iter  char   out  int i                                             For  for  loops in the old c style  int tokens found   1  delim size  line size       Calculate  line size  indirectly  without strlen   call  int start idx 100   end idx 100       Store the indexes of tokens  Example  Power    loc  P   1  loc      6   Change 100 with MAX TOKENS or use malloc   for more than 100 tokens  Example   b1 b2 b3     b200   if    out storage    NULL                   return -4     This SHOULD be NULL  Not Already Allocated if    line     delim                        return -1     NULL pointers Rejected Here if    delim size   strlen  delim       0    return -2     Delimiter not provided  start ptr   line      Start visiting input  We will distinguish tokens in a single pass  for good performance                        Then we are allocating one unified memory region  amp  doing one memory copy  while     end ptr   strstr  start ptr  delim              start idx  tokens found -1     start ptr - line       Store the Index of current token     end idx  tokens found - 1     end ptr - line          Store Index of first character that will be replaced with                                                             0   Example   arg1  arg2  end  - gt   arg1 0 arg2 0 end      tokens found                                          Accumulate the count of tokens      start ptr   end ptr   delim size                      Set pointer to the next c-string within the line    for   iter   start ptr    iter    0     iter       start idx  tokens found -1     start ptr - line       Store the Index of current token  of last token here  end idx  tokens found -1     iter - line              and the last element that will be replaced with  0  line size   iter - line       Saving CPU cycles  Indirectly Count the size of  line without using strlen     int size ptr region    1   tokens found  sizeof  char         The size to store pointers to c-strings   1   NULL   out    char    malloc  size ptr region     line size   1     5        Fit everything there   it is all memory    It reserves a contiguous space for both  char    pointers AND string region  5 Bytes for  Out of Range  tests   out storage   out        Update the char   pointer of the caller function      Out of Range  TEST  Verify that the extra reserved characters will not be changed  Assign Some Values    char  extra chars    char   out   size ptr region     line size   1      extra chars 0    1  extra chars 1    2  extra chars 2    3  extra chars 3    4  extra chars 4    5   for   i   0  i  lt  tokens found  i          Assign adresses first part of the allocated memory pointers that point to     out  i      char   out   size ptr region   start idx  i       the second part of the memory  reserved for Data  out  tokens found      char   NULL      ptr1  ptr2        ptrN   char   NULL         We just added the  char   NULL                                                        Now assign the Data  c-strings    0 terminated strings   char  str region    char   out   size ptr region      Region inside allocated memory which contains the String Data  memcpy  str region  line  line size        Copy input with delimiter characters  They will be replaced with  0     Now we should replace   arg1  arg2  arg3  with  arg1 0 arg2 0 arg3   Don t worry for characters after   0    They are not used in standard c lbraries  for  i   0  i  lt  tokens found  i    str region  end idx  i         0       Out of Range  TEST  Wait until Assigned Values are Printed back    for   int i 0  i  lt  5  i     printf  c  x    extra chars i     printf   n         out memory should now contain  example data       ptr1  ptr2     ptrN   char   NULL   token1 0    token2 0       tokenN 0   5 bytes for tests                                                                                                                                                                                                                                                   These 5 Bytes should be intact   return tokens found      int main       char in line      Arg1  Th s is not Del m ter  Arg3    Final   char delim           char   columns  int i   printf  Example1  n    columns   NULL    Should be NULL to indicate that it is not assigned to allocated memory  Otherwise return -4   int cols found   getcols  in line  delim   amp columns   for   i   0  i  lt  cols found  i     printf  Column   d      s n   i  columns  i          lt -  1st way       2nd way     for   i   0  columns  i    i    printf  start idx   d      s n   i  columns  i       free  columns         Release the Single Contiguous Memory Space  columns   NULL        Pointer   NULL to indicate it does not reserve space and that is ready for the next malloc     printf   n nExample2  Nested  n n     char example file      ID Day Month Year Telephone email Date of registration n           1 Sunday january 2009 123-124-456 jitter go xyz 2015-05-13 n           2 Monday March 2011   30 333-22-55 buffer wl it 2009-05-23    char   rows  int j   rows   NULL    getcols   requires it to be NULL   Avoid dangling pointers  leaks e t c    getcols  example file    n    amp rows   for   i   0  rows  i    i                    printf  Line   d      s n   i  rows  i              char   columnX   NULL          getcols  rows  i          amp columnX           for   j   0  columnX  j    j    printf    Col   d      s n   j  columnX  j              free  columnX             free  rows    rows   NULL   return 0

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