Add build system scaffolding and libc headers

1 files changed, 65 insertions, 0 deletions

diff --git a/lib/libc/stdio/popen.c b/lib/libc/stdio/popen.c
new file mode 100644
index 00000000..92b6a099
--- /dev/null
+++ b/lib/libc/stdio/popen.c
@@ -0,0 +1,65 @@
+#include <io.h>
+#include <errno.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+FILE *popen(const char *command, const char *mode)
+{
+	FILE *stream;
+	int oflag;
+	int pipefd[2];
+
+	switch (*mode) {
+	case 'r':
+		oflag = O_RDONLY;
+		break;
+	case 'w':
+		oflag = O_WRONLY;
+		break;
+	default:
+		errno = EINVAL;
+		return NULL;
+	}
+
+	if (pipe2(pipefd, O_CLOEXEC) < 0)
+		return NULL;
+
+	stream = fdopen(pipefd[oflag], mode);
+	if (stream == NULL) {
+		close(pipefd[0]);
+		close(pipefd[1]);
+		return NULL;
+	}
+
+	pid_t pid = fork();
+
+	if (pid < 0) {
+		close(pipefd[0]);
+		close(pipefd[1]);
+		fclose(stream);
+		return NULL;
+	} else if (pid == 0) {
+		if (oflag == O_RDONLY) {
+			dup2(pipefd[1], STDOUT_FILENO);
+			close(pipefd[0]);
+			close(pipefd[1]);
+		} else {
+			dup2(pipefd[0], STDIN_FILENO);
+			close(pipefd[0]);
+			close(pipefd[1]);
+		}
+		execl("/bin/sh", "sh", "-c", command, (char *)NULL);
+		_exit(127);
+	} else {
+		if (oflag == O_RDONLY) {
+			close(pipefd[1]);
+		} else {
+			close(pipefd[0]);
+		}
+
+		stream->pid = pid;
+
+		return stream;
+	}
+}