How can I correct this printing output issue? - c

Question

For a homework assignment, I wrote some code in C to print out the permissions and file name of the files that are stored in an achive file. My code compiles, but for some reason, the name of the second file is returned in a new line.
Here is how my output looks like in terminal:
rw-r--r-- 501/20 1-s.txt
rw-r--r-- 501/20
2-s.txt
(empty blank line here)
This is how I want the output to look:
rw-r--r-- 501/20 1-s.txt
rw-r--r-- 501/20 2-s.txt
(no empty blank line here)
Can someone take a look at my code and give me some tips on how to fix my code? I suspect it's related to the way I read and select the file name (using my_ar.ar_name), but I can't figure out how to fix it. Thank you for your time.
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/utsname.h>
#include <ctype.h>
#include <string.h>
#include <ar.h>
int main (int argc, char **argv)
{
FILE *fp;
size_t readNum;
long long tot_file_size, cur_file_size;
struct stat fileStat;
struct ar_hdr my_ar;
//open the archive file (e.g., hw.a)
fp = fopen(argv[1], "r");
if (fp == NULL)
{
perror("Error opening the file\n");
exit(-1);
}
//size of the archive file
fseek(fp, 0, SEEK_END);
tot_file_size =ftell(fp);
rewind(fp);
//read data into struct
fseek(fp, strlen(ARMAG), SEEK_SET);
file_size_cnt = 0;
while (ftell(fp) < tot_file_size - 1)
{
readNum = fread(&my_ar, sizeof(my_ar), 1, fp);
if (stat(argv[1], &fileStat) == -1) {
perror("stat");
exit(EXIT_FAILURE);
}
if ((fileStat.st_mode & S_IFMT) == S_IFREG)
{
printf( (fileStat.st_mode & S_IRUSR) ? "r" : "-");
printf( (fileStat.st_mode & S_IWUSR) ? "w" : "-");
printf( (fileStat.st_mode & S_IXUSR) ? "x" : "-");
printf( (fileStat.st_mode & S_IRGRP) ? "r" : "-");
printf( (fileStat.st_mode & S_IWGRP) ? "w" : "-");
printf( (fileStat.st_mode & S_IXGRP) ? "x" : "-");
printf( (fileStat.st_mode & S_IROTH) ? "r" : "-");
printf( (fileStat.st_mode & S_IWOTH) ? "w" : "-");
printf( (fileStat.st_mode & S_IXOTH) ? "x" : "-");
printf("%.*s", 15, my_ar.ar_name);
printf("\n");
}
cur_file_size = atoll(my_ar.ar_size);
if (fseek(fp, cur_file_size, SEEK_CUR) != 0)
{
perror("You have an error.\n");
exit(-1);
}
}
//printf("\n");
fclose(fp);
return 0;
}

Answer 1

You don't want a new line to be printed? So don't print it!
Remove this:
printf("\n");
It is placed at the end of your code.
EDIT
I gauss you don't want to remove it completely, but you want to print it anytime except the last time.
if (ftell(fp) != tot_file_size - 1) {
printf("\n");
}
EDIT V1.1
I ran your code under my linux mint 13 after my improvment. This is my output:
rw-r--r--a.txt/
rw-r--r--b.txt/
This is the format you want, isn't it?

Answer 2

There are a number of issues.
OP has if (stat(argv[1], &fileStat) == -1) ... which is curious to repeatedly query the file status of the "file name of the files" rather than the file name in my_ar.ar_name. Thus the same file stats will appear.
The first use of printf("%.*s", 15, my_ar.ar_name) gave "501/20 1-s.txt". This looks like an unusual file name. The ar_name field is "If the file member name fits, the ar_name field contains the name directly, and is terminated by a slash (/) and padded with blanks on the right. If the member's name does not fit, ar_name contains a slash (/) followed by a decimal representation of the name's offset in the archive string table described below." So the presence of / implies you have more to do to extract the file name. It also may be that the fields are not NUL byte terminated. OP needs to read up on struct ar_hdr. Try: http://www.lehman.cuny.edu/cgi-bin/man-cgi?ar.h+3
The extracted filename, done errantly in this code, may or may not contain surprising bytes. I am certain this is why you saw an unexpected end-of-line in the 2nd line of output. Testing the filename for printable ASCII char is prudent. isprint()