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Read lines from file, tokenise them, save data into an array of structs.
Character Strings example from a Well House Consultants training course
More on Character Strings [link]
Source code: s4.c Module: C206
#include <stdio.h>
#include <string.h> #include <stdlib.h> typedef struct { char tlc[4]; float lati; float longi; char placename[61]; int p2005; } Station, *Depot; /* Combined example - reads a whole file line by line and creates a structure for each od the lines; stores pointers to each of the lines in an array. A fairly typical example of initial data setup. */ main () { Depot ourlocal[3000]; // Allow up to 3000 stations // For "production" code would use calloc and realloc to make size dynamic // but in this example I was keeping code a bit easier to follow int nstations = 0; Depot Current; FILE * datasource; char lynes[161]; datasource = fopen("railstats.xyz","r"); while (fgets(lynes,160,datasource)) { Current = malloc(sizeof(Station)); /* Allocate memory a station */ int passengers[6]; char *four_code = strtok(lynes,"\t"); char *tlc = strtok(NULL,"\t"); strncpy(Current->tlc,tlc,3); // Safe copy, limiting at 3 charater string Current->tlc[3] = '\0'; char *postcode = strtok(NULL,"\t"); char *osref = strtok(NULL,"\t"); char *lati = strtok(NULL,"\t"); char *longi = strtok(NULL,"\t"); char *placename = strtok(NULL,"\t"); strncpy(Current->placename, placename, 60); // Safe copy (do not use strcpy!) int k; int complete = 1; for (k=0; k<6; k++) { char *nextnum = strtok(NULL,"\t"); // Check if we really do have numbers for each year if (! nextnum) { complete = 0; continue; } if (nextnum[0] < '1' || nextnum[0] > '9') { complete = 0; continue; } passengers[k] = atoi(nextnum); } Current->p2005 = passengers[2]; // If the record is complete, store it. // But if it's no good, release the memory if (complete) { Current->lati = atof(lati); Current->longi = atof(longi); ourlocal[nstations++] = Current; } else { free(Current); /* Avoid memory being lost (leaked) */ } } // Having set the data structure up (the real purpose of this demo), // do something to actually make use of it ;-) int k; for (k=0; k<nstations; k++) { Current = ourlocal[k]; printf("%3s / %s\n",(*Current).tlc,(*Current).placename); printf("%3s / %s\n",Current->tlc,Current->placename); /* Same Thing! */ } } Learn about this subject
This module and example are covered on the following public courses:
* Learning to Program in C * Learning to program in C and C++ * Programming in C * C and C++ Programming * Learning to program in C and C++ * C and C++ Programming Also available on on site courses for larger groups Books covering this topic
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Other Examples
This example comes from our "Character Strings" training module. You'll find a description of the topic and some
other closely related examples on the "Character Strings" module index page.
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