为什么不能用popen方法沟通mpg123的？ [英] Why won't popen communicate with mpg123?
问题描述
我在写我的覆盆子PI的媒体服务器。我能够创建一个使用的popen通过一个遥控器来控制omxplayer程序。
I'm writing a media server for my raspberry pi. I was able to create a program which uses popen to control omxplayer via a remote control.
我现在想控制音乐mpg123的。我采取了同样的code，在omxplayer程序与工作的popen并将其应用到mpg123的，但它不工作。它启动，但不会承认发送给它的任何输入。我不知道为什么人们会工作，其他的不会的。
I would now like to control mpg123 for music. I took the same code that worked in the omxplayer program with popen and applied it to mpg123, but it isn't working. It starts up, but won't acknowledge any input sent to it. I don't know why one would work and the other wouldn't.
下面是我的code：
void play_music (char *list, int random)
{
FILE *pp;
char c;
char command[501];
struct stat buf;
if(access(list, R_OK) == -1)
{
fprintf(stderr, "%s: play_music: access failed (%s) (%s)\n", program_name, strerror(errno), list);
exit(EXIT_FAILURE);
}
if(stat(list, &buf) == -1)
{
fprintf(stderr, "%s: play_music: stat failed (%s) (%s)\n", program_name, strerror(errno), list);
exit(EXIT_FAILURE);
}
strcpy(command, "/usr/bin/mpg123 -C ");
if(random == 1)
strcat(command, "-z ");
if(S_ISREG(buf.st_mode) == 1)
{
strcat(command, "-@ ");
strcat(command, list);
}
else if(S_ISDIR(buf.st_mode) == 1)
{
strcat(command, list);
if(list[strlen(list) - 1] != '*')
{
if(list[strlen(list) - 1] != '/')
strcat(command, "/");
strcat(command, "*");
}
}
else
{
fprintf(stderr, "%s: play_music: stat reported unknown (%s)\n", program_name, list);
exit(EXIT_FAILURE);
}
strcat(command, " > /dev/null 2>&1");
if((pp = popen(command, "w")) == NULL)
{
fprintf(stderr, "%s: play_music popen failed (%s)\n", program_name, strerror(errno));
exit(EXIT_FAILURE);
}
while((c = get_code()))
{
if(system("pidof mpg123 > /dev/null") != 0)
return;
switch(c)
{
case 31:
fputc('f', pp);
break;
case 32:
fputc('d', pp);
break;
case 33:
fputc('s', pp);
break;
case 34:
fputc('q', pp);
}
if(fflush(pp) == EOF)
{
fprintf(stderr, "%s: play_music fflush failed (%s)\n", program_name, strerror(errno));
exit(EXIT_FAILURE);
}
}
}
我一直在试图算出这个时间太长了，可以有人请帮助！
I've been trying to figure this out for far too long, can someone please help!
注：
-
的get_ code（）是在此基础上遥控按钮返回一个int一个工作函数pressed。
get_code() is a working function that returns an int based on which remote control button is pressed.
变量列表可以是一个目录路径或播放列表的文件名。
The variable 'list' is either a directory path or a playlist filename.
变量随机是一个int标志（1随机播放）。
The variable 'random' is an int flag (1 for random play).
推荐答案
由于J.F.塞巴斯蒂安在评论中表示，提供了一个伪终端自己原来是什么，我需要做的。创建一个伪终端行事像从键盘输入来为所需要的工作。
As J.F. Sebastian stated in the comments, "provide a pseudo-tty yourself" turned out to be what I needed to do. Creating a pseudo terminal to act like the input came from the keyboard is what is needed to work.
下面是修改code：
void play_music (char *playlist, int random)
{
char c;
int fdm;
int fds = 0;
int x = 0;
pid_t pid;
char *flag1 = "/usr/bin/mpg123";
char *flag2 = "-C";
char *flag3 = "-z";
char *flag4 = "-@";
char *flag5 = TEMP_FILE; // /tmp/temp_playlist.pls
char *slave_name;
char *argv[6];
struct stat buf;
if(stat(playlist, &buf) == -1)
{
fprintf(stderr, "%s: play_music: stat failed (%s) (%s)\n", program_name, strerror(errno), playlist);
exit(EXIT_FAILURE);
}
if((fdm = posix_openpt(O_RDWR)) == -1)
{
fprintf(stderr, "%s: posix_openpt failed (%s)\n", program_name, strerror(errno));
exit(EXIT_FAILURE);
}
if(grantpt(fdm) == -1)
{
fprintf(stderr, "%s: grantpt failed (%s)\n", program_name, strerror(errno));
close(fdm);
exit(EXIT_FAILURE);
}
if(unlockpt(fdm) == -1)
{
fprintf(stderr, "%s: unlockpt failed (%s)\n", program_name, strerror(errno));
close(fdm);
exit(EXIT_FAILURE);
}
if((slave_name = ptsname(fdm)) == NULL)
{
fprintf(stderr, "%s: ptsname failed\n", program_name);
close(fdm);
exit(EXIT_FAILURE);
}
if((pid = fork()) == -1)
{
fprintf(stderr, "%s: fork failed (%s)\n", program_name, strerror(errno));
close(fdm);
exit(EXIT_FAILURE);
}
if(pid == 0) // Child
{
if(setsid() == -1)
{
fprintf(stderr, "%s: setsid failed (%s)\n", program_name, strerror(errno));
close(fdm);
exit(EXIT_FAILURE);
}
if((fds = open(slave_name, O_RDWR)) == -1)
{
fprintf(stderr, "%s: open failed (%s)\n", program_name, strerror(errno));
close(fdm);
exit(EXIT_FAILURE);
}
if(dup2(fds, STDIN_FILENO) == -1)
{
fprintf(stderr, "%s: dup2(1) failed (%s)\n", program_name, strerror(errno));
close(fdm);
close(fds);
exit(EXIT_FAILURE);
}
if(dup2(fds, STDOUT_FILENO) == -1)
{
fprintf(stderr, "%s: dup2(2) failed (%s)\n", program_name, strerror(errno));
close(fdm);
close(fds);
exit(EXIT_FAILURE);
}
if(dup2(fds, STDERR_FILENO) == -1)
{
fprintf(stderr, "%s: dup2(3) failed (%s)\n", program_name, strerror(errno));
close(fdm);
close(fds);
exit(EXIT_FAILURE);
}
argv[x++] = flag1;
argv[x++] = flag2;
if(random == 1)
argv[x++] = flag3;
argv[x++] = flag4;
if(S_ISREG(buf.st_mode) == 1)
argv[x++] = playlist;
else if(S_ISDIR(buf.st_mode) == 1)
{
if(make_playlist(playlist) == RETURN_FAILURE)
{
fprintf(stderr, "%s: play_music: make_playlist failed (%s)\n", program_name, playlist);
close(fdm);
close(fds);
exit(EXIT_FAILURE);
}
argv[x++] = flag5;
}
else
{
fprintf(stderr, "%s: play_music: stat reported unknown (%s)\n", program_name, playlist);
close(fdm);
close(fds);
exit(EXIT_FAILURE);
}
argv[x++] = NULL;
if(execv("/usr/bin/mpg123", argv) == -1)
{
fprintf(stderr, "%s: execv failed (%s)\n", program_name, strerror(errno));
close(fdm);
close(fds);
exit(EXIT_FAILURE);
}
}
else // Parent
{
while((c = get_code()) != 31)
{
switch(c)
{
case 30:
case 19:
write(fdm, " ", 1);
break;
case 20: // Up
write(fdm, "+", 1);
break;
case 22: // Down
write(fdm, "-", 1);
break;
case 21: // Right
write(fdm, "f", 1);
break;
case 23: // Left
write(fdm, "d", 1);
break;
}
}
write(fdm, "q", 1);
wait(&pid);
close(fdm);
if(fds != 0)
close(fds);
}
}
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