Question

I have a program that walks the file system hierarchy listing the file path names on a binary file as follows:

struct list_rec{
    int seqno;
    int path_length;
    char *file_path;
};
FILE *listoffiles;
int no_of_files;/*couter to keep track of files visited*/
static int list_the_files(const char *fpath,const struct stat *sb, int tflag, struct   FTW *ftwbuf)
{
struct list_rec t;
 no_of_files = no_of_files+1;
 t.seqno = no_of_files;
 t.path_length = strlen(fpath);
 t.file_path = malloc((sizeof(char)*t.path_length)+1);
 strcpy(t.file_path,fpath);

 fwrite(&t.seqno,sizeof(int),1,listoffiles);
 fwrite(&t.path_length,sizeof(int),1,listoffiles);
 fwrite(t.file_path,t.path_length,1,listoffiles);

 free(t.file_path);

 return 0;
}

int main(int argc, char *argv[])
{
 listoffiles = fopen("/home/juggler/Examples/Traces/files.txt","r+b");
 no_of_files = 0;
 ftw(argv[1],list_the_files,20);
}

and then read the file to check from a different program in the following way:

struct list_rec{
    int seqno;
    int path_length;
    char *file_path;
};
FILE *listoffiles;
int main()
{
    struct list_rec t;

    listoffiles = fopen("/home/juggler/Examples/Traces/files.txt","rb");
    if(!listoffiles)
    {
            printf("Unable to open file");
            return 1;
    }



    while(fread(&t.seqno,sizeof(int),1,listoffiles)!=0)
    {
    printf("\n %d  ",t.seqno);/*Log Record Number*/
    fread(&t.path_length,sizeof(int),1,listoffiles);
            printf(" %d",t.path_length);
    t.file_path = malloc(sizeof(char)*t.path_length);
            fread(t.file_path,t.path_length,1,listoffiles);
            printf(" %s",t.file_path);

    fflush(stdout);
    }
}

My problem is the output on running the second program shows some unwanted characters appended to some of the filepaths as follows:check record 51611 and 51617

51611   92 /media/New Volume/ March2010/June_2009/new latex_12 may 2009/document6_new.pdf��
51612   99 /media/New Volume/ March2010/June_2009/new latex_12 may 2009/proof with graph.tex.sav
51613   115 /media/New Volume/ March2010/June_2009/new latex_12 may 2009/Operations beyond read and write.tex.bak
51614   107 /media/New Volume/ March2010/June_2009/new latex_12 may 2009/singe version implementation.blg
51615   93 /media/New Volume/ March2010/June_2009/new latex_12 may 2009/formalization1.pdf
51616   92 /media/New Volume/ March2010/June_2009/new latex_12 may 2009/document6_new.texÉ… 
51617   95 /media/New Volume/ March2010/June_2009/new latex_12 may 2009/cascading undone.tex

Answer 1

You’re not null-terminating the file paths when you read them back in.

You should be allocating one more char’s worth than the string length, and setting that last char to 0 (fread won’t do that for you).