Victor Leite
Reputation: 21
C stdin does not work
I trying to fix some bugs in a legacy code. This is the code:
#include <stdio.h>
#include <string.h>
#include <pthread.h>
#include <sys/msg.h>
#include "libSvr.h"
#define CONEC 3
#define CONFIG 4
typedef struct {
long type;
int cmd;
int id;
char data[7000];
} msg;
typedef struct {
int id[100];
unsigned long ip[100];
int type[100];
char name[100][20];
int num;
} conec;
typedef struct {
char ip;
char svr;
} param_cfg;
typedef struct {
unsigned long my_ip;
unsigned long svr_ip;
} tcp_cfg;
msg client, server;
conec conec_tab;
param_cfg param;
tcp_cfg setup;
void *Receive_MSG(void *arg) {
int i;
while (1) {
if ( msgrcv(msgkey,&client,7008,2,0) != -1 ) {
switch (client.cmd) {
case CONEC:
memmove((char*)&conec_tab,client.data,sizeof(conec_tab));
printf("\n%d\n",conec_tab.num);
break;
case CONFIG:
switch (conec_tab.type[client.id]) {
case 0:
memmove((char*)¶m,&client.data[sizeof(param_cfg)],sizeof(param_cfg));
printf("------------PARAM Config------------\n");
printf("%c\n%c\n\n",param.ip,param.svr);
break;
case 1:
memmove((char*)&setup,client.data,sizeof(tcp_cfg));
printf("\n------------Setup------------\n");
printf("%s\n",Inet_ntoa(setup.my_ip));
break;
}
}
}
}
}
void send_msg() {
msgsnd(msgkey,&(server.type),7008,0);
}
void Process(char *command) {
server.type = 1;
if ( !strncmp(command,"text",8) ) {
server.cmd = 1;
send_text();
send_msg();
}
else if ( !strncmp(command,"image",9) ) {
server.cmd = 2;
send_image();
send_msg();
}
else
printf("\nCommand not found.\n");
}
int main()
{
int i;
char cmd[100];
msgkey=msgget(100,0);
if ( msgkey == -1) {
printf("ERROR msgkey!!");
exit(1);
}
pthread_t receive;
pthread_create(&receive,NULL,Receive_MSG,NULL);
do {
printf("Enter a command -> ");
if (fgets(cmd,100,stdin) == NULL) {
printf("error");
exit(1);
}
cmd[strlen(cmd)-1]='\0';
if ( (strcmp(cmd,"exit")) && (strcmp(cmd,"")) )
Process(cmd);
} while (strcmp(cmd,"exit"));
return 0;
}
The libSvr.h code:
#ifndef LIBSVR_H
#define LIBSVR_H
#pragma pack(push,1)
#pragma pack(1)
extern "C" void send_text();
extern "C" void send_image();
#pragma pack(pop)
#endif
The thread receive just receive some messages from another application in the queue id msgkey and print some text.
The problem is when I get into the do while loop, where I need to get some user inputs, the fgets fails... When I printed the error (with errno) I saw that it is a bad file descriptor error (EBADF).
The Process function get the command a calls the appropriate function, that basically will send some data through a socket. And these functions called by Process are from a lib (libSvr) writen in C++ with functions C extern-ed.
I'm using an ubuntu 12.10 machine with gcc 4.7.2.
I tried to see the code after preprocessor (with gcc -E) and stdin is still showed as stdin. I tried to print the output of fileno(stdin) and it was 0 (I saw somewhere that it the right value) and then I tried to call fgets this way: fgets(cmd,100,0). But nothing works.
Anyone have any idea of what is happening?
Thanks!
Edit:
Included all the code.
I tried call gets(), scanf() and read() and also comment the thread creation (pthread_create) but nothing changed.
I ran the command strace -s2000 -etrace=open,close <MYPROGRAM> and this is the output:
open("/mnt/hgfs/projects/tls/i686/sse2/cmov/libSvr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/mnt/hgfs/projects/tls/i686/sse2/libSvr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/mnt/hgfs/projects/tls/i686/cmov/libSvr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/mnt/hgfs/projects/tls/i686/libSvr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/mnt/hgfs/projects/tls/sse2/cmov/libSvr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/mnt/hgfs/projects/tls/sse2/libSvr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/mnt/hgfs/projects/tls/cmov/libSvr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/mnt/hgfs/projects/tls/libSvr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/mnt/hgfs/projects/i686/sse2/cmov/libSvr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/mnt/hgfs/projects/i686/sse2/libSvr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/mnt/hgfs/projects/i686/cmov/libSvr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/mnt/hgfs/projects/i686/libSvr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/mnt/hgfs/projects/sse2/cmov/libSvr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/mnt/hgfs/projects/sse2/libSvr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/mnt/hgfs/projects/cmov/libSvr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/mnt/hgfs/projects/libSvr.so.1", O_RDONLY|O_CLOEXEC) = 3
close(3) = 0
open("/mnt/hgfs/projects/libpthread.so.0", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
close(3) = 0
open("/lib/i386-linux-gnu/libpthread.so.0", O_RDONLY|O_CLOEXEC) = 3
close(3) = 0
open("/mnt/hgfs/projects/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/lib/i386-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
close(3) = 0
open("/mnt/hgfs/projects/libstdc++.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/usr/lib/i386-linux-gnu/libstdc++.so.6", O_RDONLY|O_CLOEXEC) = 3
close(3) = 0
open("/mnt/hgfs/projects/libgcc_s.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/lib/i386-linux-gnu/libgcc_s.so.1", O_RDONLY|O_CLOEXEC) = 3
close(3) = 0
open("/mnt/hgfs/projects/libm.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/lib/i386-linux-gnu/libm.so.6", O_RDONLY|O_CLOEXEC) = 3
close(3) = 0
close(0) = 0
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
close(0) = -1 EBADF (Bad file descriptor)
Enter a command ->
errorEnter a command ->
errorEnter a command ->
errorEnter a command ->
So, the stdin file descriptor is beeing closed but and now I need to know where it is beeing closed.
I'm studying some howto's and the man page of strace now, because I never use it before.
Any help and tips will be welcome.
Thanks again!
Upvotes: 1
Views: 753
Answers (1)
Atle
Reputation: 1877
I got your code to run with a few changes. I did not manage to get the System V-stuff to work, but I got it to read commands without crashing.
I think the initialization of System V-stiff in your program is wrong, and creates undefined behavior.
All the close(0)-s is probably from the server-thread somewhere, which does not break from the while-loop on errors.
The initialization of System V (I have no clue how to use this, really, just read man-pages), I did like this:
// msg_key is declared above the server-code (used by both) like `key_t msg_key`
msg_key = ftok ("/home/atle/prog/test.c", 'A');
if (msg_key == -1) {
printf ("ftok error: %s\n", strerror(errno));
exit(1);
}
msgkey = msgget(msg_key, IPC_CREAT);
if ( msgkey == -1) {
printf ("msgget error: %s\n", strerror(errno));
exit(1);
}
In the server, I did like this:
int msgkey_server = msgget(msg_key, 0);
if ( msgkey_server == -1) {
printf ("Server msgget error: %s\n", strerror(errno));
exit(1);
}
while (1) {
printf ("Server loop\n");
if ( msgrcv(msgkey_server,&client,sizeof(client),0,0) == -1 ) {
printf ("Server read error: %s\n", strerror(errno));
exit(1);
}
else {
// MSG READ OK
}
BTW:
When you pass a struct to a command with its size attached, you should always user sizeof() like I did here, not writing the size manually (causes problems).
Extra BTW:
You need the errno-header:
#include <errno.h>
Upvotes: 1
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