Impl working C solution
Messy, but it appears to work with the test.csv. Formatted with `clang-format --style=Google`.
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3 changed files with 275 additions and 2 deletions
4
c_impl/.gitignore
vendored
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4
c_impl/.gitignore
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compile_commands.json
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.cache/
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src/*.o
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fields_from_csv
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@ -1,3 +1,265 @@
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int main(int argc, char **argv) {
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return 0;
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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typedef struct StrDList {
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char *string;
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struct StrDList *next;
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struct StrDList *prev;
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} StrDList;
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typedef struct ParsedArgs {
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const char *input_filename;
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StrDList *fields;
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int usage_printed;
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int error;
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} ParsedArgs;
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void usage() {
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puts(
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"USAGE:\n"
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"./fields_from_csv <input_csv> <field> [<field>...]\n");
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}
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StrDList *create_strdlist() { return calloc(1, sizeof(StrDList)); }
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void append_strdlist(StrDList *head, const char *string) {
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StrDList *current = head;
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while (current->next) {
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current = current->next;
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}
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current->next = calloc(1, sizeof(StrDList));
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current->next->prev = current;
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size_t string_size = strlen(string);
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current->next->string = malloc(string_size + 1);
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memcpy(current->next->string, string, string_size);
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current->next->string[string_size] = 0;
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}
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void cleanup_strdlist(StrDList **head) {
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StrDList *current = *head;
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while (current->next) {
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current = current->next;
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}
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if (*head == current) {
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return;
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}
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while (current->prev) {
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current = current->prev;
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if (current->next->string) {
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free(current->next->string);
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}
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free(current->next);
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current->next = NULL;
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}
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(*head)->next = NULL;
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free(*head);
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*head = NULL;
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}
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size_t print_and_count_strdlist(StrDList *head) {
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size_t count = 0;
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StrDList *current = head;
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puts("Printing strdlist...");
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while (current->next) {
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current = current->next;
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printf("%s ", current->string);
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++count;
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}
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printf("\n");
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return count;
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}
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int strdlist_has_str(StrDList *head, const char *str) {
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StrDList *current = head;
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int idx = 0;
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while (current->next) {
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current = current->next;
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if (strcmp(current->string, str) == 0) {
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return idx;
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} else {
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++idx;
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}
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}
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return -1;
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}
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ParsedArgs parse_args(int argc, char **argv) {
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// init
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ParsedArgs args;
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args.input_filename = NULL;
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args.fields = create_strdlist();
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args.usage_printed = 0;
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args.error = 0;
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--argc;
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++argv;
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// get filename and field from args
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if (argc > 1) {
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args.input_filename = argv[0];
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} else {
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args.error = 1;
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usage();
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args.usage_printed = 1;
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}
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--argc;
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++argv;
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while (argc > 0) {
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append_strdlist(args.fields, argv[0]);
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--argc;
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++argv;
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}
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return args;
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}
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typedef struct CSVEntry {
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char *buf;
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size_t idx;
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int is_end_of_line;
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int is_end_of_file;
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int is_chosen_field;
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} CSVEntry;
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CSVEntry get_field(FILE *fd, size_t field_idx) {
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size_t current_size = 512;
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CSVEntry entry;
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entry.is_end_of_line = 0;
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entry.is_end_of_file = 0;
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entry.is_chosen_field = 0;
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entry.buf = NULL;
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size_t idx = 0;
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int next = fgetc(fd);
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while (next != EOF) {
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if (next == ',') {
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break;
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} else if (next == '\n') {
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entry.is_end_of_line = 1;
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break;
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} else if (next == ' ' || next == '\t') {
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next = fgetc(fd);
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continue;
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}
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if (!entry.buf) {
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// malloc of buf deferred to here in case a field reaches EOF
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entry.buf = malloc(current_size);
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}
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entry.buf[idx++] = next;
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if (idx >= current_size) {
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current_size *= 2;
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entry.buf = realloc(entry.buf, current_size);
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}
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next = fgetc(fd);
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}
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if (next == EOF) {
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entry.is_end_of_file = 1;
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}
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if (entry.buf) {
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if (idx >= current_size) {
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current_size += 1;
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entry.buf = realloc(entry.buf, current_size);
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entry.buf[idx] = 0;
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} else {
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entry.buf[idx] = 0;
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}
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}
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entry.idx = field_idx;
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return entry;
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}
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int main(int argc, char **argv) {
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ParsedArgs args = parse_args(argc, argv);
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if (args.error) {
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return 1;
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} else if (args.usage_printed) {
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return 0;
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}
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size_t field_count = print_and_count_strdlist(args.fields);
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FILE *csv_fd = fopen(args.input_filename, "r");
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if (!csv_fd) {
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printf("ERROR: Failed to open %s!\n", args.input_filename);
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return 2;
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}
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size_t cols_size = 32;
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CSVEntry *entries = calloc(cols_size, sizeof(CSVEntry));
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// get first row of fields and mark the picked ones out of them
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size_t idx = 0;
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while (1) {
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entries[idx] = get_field(csv_fd, idx);
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++idx;
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if (idx >= cols_size) {
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// dynamically resize if more space is needed
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cols_size *= 2;
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entries = realloc(entries, cols_size * sizeof(CSVEntry));
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memset(entries + (cols_size / 2), 0, cols_size / 2);
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}
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// mark entry if it is specified entry
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if (strdlist_has_str(args.fields, entries[idx - 1].buf) >= 0) {
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printf("Found chosen field at idx %ld\n", idx - 1);
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entries[idx - 1].is_chosen_field = 1;
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}
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// break if end of first line is reached
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// TODO maybe check for the case where there is a newline immediately
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// after a comma
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if (entries[idx - 1].is_end_of_line) {
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break;
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}
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}
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// do printing of only the chosen columns
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idx = 0;
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while (1) {
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CSVEntry entry = get_field(csv_fd, idx);
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if (entries[idx].is_chosen_field && entry.buf) {
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printf("%s, ", entry.buf);
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}
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if (entry.buf) {
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free(entry.buf);
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}
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if (entry.is_end_of_file) {
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break;
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} else if (entry.is_end_of_line) {
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idx = 0;
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printf("\n");
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} else {
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++idx;
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}
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}
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fclose(csv_fd);
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for (size_t i = 0; i < field_count; ++i) {
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if (entries[i].buf) {
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free(entries[i].buf);
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}
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}
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free(entries);
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cleanup_strdlist(&args.fields);
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return 0;
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}
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7
c_impl/test.csv
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7
c_impl/test.csv
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one, two , three , four , five
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1, 2, 3, 4, 5
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1, 2, 3, 4, 5
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10, 20, 30, 40 , 50
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10, 20, 30, 40 , 50
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10, 20, 30, 40 , 50
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10, 20, 30, 40 , 50
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