Csv

# 4. Csv

The csv(3m) module parses the popular comma separated values (CSV) format exported by applications like spreadsheets. This parser considers quoted elements, quoted quotes, and preserves carriage returns and newlines within elements.

Example 1. Reading /etc/passwd
The following example uses csv(3m) to parse the `/etc/passwd` file and print the username and uid of each user.

      #include <stdlib.h>
      #include <stdio.h>
      #include <mba/csv.h>

      int
      main(int argc, char *argv[])
      {
          FILE *in;
          char buf[1024];
          char *row[10];
          int n;

          in = fopen("/etc/passwd", "r");

          while ((n = csv_row_fread(in, buf, 1024, row, 10, ':', CSV_TRIM)) > 0) {
              printf("%s %s\n", row[0], row[2]);
          }
          fclose(in);

          return EXIT_SUCCESS;
      }

Please note that escaping a quote requires that the whole element to be quoted as well. So a quoted string element would actually look like `"""foo"""` where the outer quotes quote the element and the remaining quote pairs are each an escape followed by the literal quote. This is consistent with how Excel and gnumeric behave and deviating from this behavior will generate an error.

### 4.1. Csv functions

The `csv_row_parse` function
Synopsis

      #include <mba/csv.h>
      int csv_row_parse(const tchar *src,
               size_t sn,
               tchar *buf,
               size_t bn,
               tchar *row[],
               int rn,
               int sep,
               int flags)

Description
Parse a line of text at `src` for no more than `sn` bytes and place pointers to zero terminiated strings allocated from no more than `bn` bytes of the memory at `buf` into the array `row` for at most `rn` data elements. The `sep` parameter must specify a separator to use and should not be a quote, carriage return, or newline. Comma ',', tab '\t', colon ':', and pipe '|' are common separators.

The `flags` parameter can be zero or any combination of `CSV_TRIM` and `CSV_QUOTES`. If `CSV_TRIM` is specified, strings will be trimmed of leading and trailing whitespace. If the `CSV_QUOTES` flag is spcecified, quotes will be interpreted. Both flags should usually be specified although it is not uncommon to encounter tab delimited files where quotes should not be interpreted.

The `csv_row_parse` function is actually a macro for either `csv_row_parse_str` or `csv_row_parse_wcs`. The `csv_row_parse_wcs` function has the same prototype but accepts `wchar_t` parameters whereas `csv_row_parse_str` accepts `unsigned char` parameters.
Returns
The `csv_row_parse` function returns the number of bytes of `src` parsed or -1 if an error occured in which case `errno` will be set appropriately.

The `csv_row_fread` function
Synopsis

      #include <mba/csv.h>
      int csv_row_fread(FILE *in, char *buf, size_t bn, char *row[], int numcols, int sep, int flags)

Description
Read a line of text from the stream `in`, process the line with `csv_row_parse` and place pointers to zero terminiated strings allocated from no more than `bn` bytes of the memory at `buf` into the array `row` for at most `rn` data elements.
Returns
The `csv_row_fread` function returns the number of bytes read from the stream `in` or -1 if an error occured in which case `errno` will be set appropriately.

Copyright 2003 Michael B. Allen <mba2000 ioplex.com>