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;[email protected];1980.05.13 2;Jerzy;Nowak;ul. Konopnicka;13a/3;00-900;Lichowice;(55)333-44-55;[email protected];1990.03.23 

And I need to read this in C. I have some code, but only for the connection.

Answer 1

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 

Answer 2

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 <http://w...content-available-to-author-only...u.org/licenses/>.  */   #include <stdio.h> #include <string.h> #include <stdlib.h>   /* 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 & 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" -> "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 < 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 < 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 < 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, &columns); for ( i = 0; i < cols_found; i++ ) printf("Column[ %d ] = %s\n", i, columns[ i ] );  //<- (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;[email protected];2015-05-13\n"         "2;Monday;March;2011;(+30)333-22-55;[email protected];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", &rows); for ( i = 0; rows[ i ]; i++) {     {         printf("Line[ %d ] = %s\n", i, rows[ i ] );         char **columnX = NULL;         getcols( rows[ i ], ";", &columnX);         for ( j = 0; columnX[ j ]; j++) printf("  Col[ %d ] = %s\n", j, columnX[ j ] );         free( columnX );     } }  free( rows ); rows = NULL;  return 0; }