Reading Space Delimited Strings Line by Line and Storing Them in Arrays (in C) -
this question has answer here:
i have input file consisting of:
createhall "red-hall" "stardust" 24 20 createhall "orange-hall" "last_samurai" 10 20 and want store each line in array future uses.
so far code is: (added lots of printf's debugging purposes.)
#include <stdio.h> #include <stdlib.h> struct str { char *commands[5]; }; struct str a[]; int main() { int i=0; int j=0; char *token; printf("starting program...\n"); char filename[] = "input.txt"; file *file = fopen ( filename, "r" ); if (file != null) { char line [1000]; printf("read new line...\n"); while(fgets(line,sizeof line,file)!= null) /* read line file */ { j=0; printf("%s\n",line); printf("start token stuff...\n"); /* first token */ token = strtok(line, " "); /* walk through other tokens */ while( token != null ) { a[i].commands[j]=token; printf( "stored command : %s\n", token ); token = strtok(null, " "); j++; } i++; } fclose(file); } else { perror(filename); //print error message on stderr. } printf("finished processing tokens...\n\n\n"); printf("%s\n%s\t%s\t%s\t%s\n", a[0].commands[0], a[0].commands[1],a[0].commands[2],a[0].commands[3],a[0].commands[4]); printf("%s\n%s\t%s\t%s\t%s\n", a[1].commands[0], a[1].commands[1],a[1].commands[2],a[1].commands[3],a[1].commands[4]); return 0; } the output on console this:
starting program... read new line... createhall "red-hall" "stardust" 24 20 start token stuff... stored command : createhall stored command : "red-hall" stored command : "stardust" stored command : 24 stored command : 20 createhall "orange-hall" "last_samurai" 10 20 start token stuff... stored command : createhall stored command : "orange-hall" stored command : "last_samurai" stored command : 10 stored command : 20 finished processing tokens... createhall "orange-hall" l" murai" ai" createhall "orange-hall" "last_samurai" 10 20 i'm not c, (this small part of assignment) believe error in
a[i].commands[j]=token; line, since before reads words fine.
thanks in advance.
from the man
return value
the strtok() , strtok_r() functions return pointer next token, or null if there no more tokens.
so pointers storing addresses of char lib[1000], that, @ end of process, contain last line read.
take note defined bad array, without dimension:
struct str a[]; should be, @ least,
struct str a[2]; the fastest correction can be:
#define _bsd_source #include <stdio.h> #include <stdlib.h> #include <string.h> struct str { char *commands[5]; }; struct str a[2]; int main() { int i=0; int j=0; char *token; printf("starting program...\n"); char filename[] = "input.txt"; file *file = fopen ( filename, "r" ); if (file != null) { char line [1000]; printf("read new line...\n"); while(fgets(line,sizeof line,file)!= null) /* read line file */ { j=0; printf("%s\n",line); printf("start token stuff...\n"); /* first token */ token = strtok(line, " "); /* walk through other tokens */ while( token != null ) { char *temp = strdup(token); if (temp != null) { a[i].commands[j]=temp; } else { fprintf(stderr, "no memory available store string\n"); return 1; } printf( "stored command : %s\n", token ); token = strtok(null, " "); j++; } i++; } fclose(file); } else { perror(filename); //print error message on stderr. } printf("finished processing tokens...\n\n\n"); printf("%s\n%s\t%s\t%s\t%s\n", a[0].commands[0], a[0].commands[1],a[0].commands[2],a[0].commands[3],a[0].commands[4]); printf("%s\n%s\t%s\t%s\t%s\n", a[1].commands[0], a[1].commands[1],a[1].commands[2],a[1].commands[3],a[1].commands[4]); return 0; } in more complex project, duplicated strings must freed due heap allocation performed strdup.
another solution can implemented using malloc , allocating space each element , using strcpy copy token.
#include <stdio.h> #include <stdlib.h> #include <string.h> struct str { char *commands[5]; }; struct str a[2]; int main() { int i=0; int j=0; char *token; printf("starting program...\n"); char filename[] = "input.txt"; file *file = fopen ( filename, "r" ); if (file != null) { char line [1000]; printf("read new line...\n"); while(fgets(line,sizeof line,file)!= null) /* read line file */ { j=0; printf("%s\n",line); printf("start token stuff...\n"); /* first token */ token = strtok(line, " "); /* walk through other tokens */ while( token != null ) { a[i].commands[j] = malloc(strlen(token)+1); if (a[i].commands[j] != null) { strcpy(a[i].commands[j], token); } else { fprintf(stderr, "no memory available store string\n"); return 1; } printf( "stored command : %s\n", token ); token = strtok(null, " "); j++; } i++; } fclose(file); } else { perror(filename); //print error message on stderr. } printf("finished processing tokens...\n\n\n"); printf("%s\n%s\t%s\t%s\t%s\n", a[0].commands[0], a[0].commands[1],a[0].commands[2],a[0].commands[3],a[0].commands[4]); printf("%s\n%s\t%s\t%s\t%s\n", a[1].commands[0], a[1].commands[1],a[1].commands[2],a[1].commands[3],a[1].commands[4]); return 0; } same thing here, should freed mallocated memory.
Comments
Post a Comment