diff options
Diffstat (limited to 'coreutils/nohup.c')
| -rw-r--r-- | coreutils/nohup.c | 188 |
1 files changed, 188 insertions, 0 deletions
diff --git a/coreutils/nohup.c b/coreutils/nohup.c new file mode 100644 index 000000000..407cf00ea --- /dev/null +++ b/coreutils/nohup.c @@ -0,0 +1,188 @@ +/* vi: set sw=4 ts=4: */ +/* nohup -- run a command immune to hangups, with output to a non-tty + Copyright (C) 2003, 2004, 2005 Free Software Foundation, Inc. + + Licensed under the GPL v2, see the file LICENSE in this tarball. + + */ + +/* Written by Jim Meyering */ +/* initial busybox port by Bernhard Fischer */ + +#include <stdio_ext.h> /* __fpending */ +#include <stdio.h> +#include <unistd.h> +#include <fcntl.h> +#include <sys/types.h> +#include <signal.h> +#include <errno.h> + +#include "busybox.h" +#define EXIT_CANNOT_INVOKE (126) +#define NOHUP_FAILURE (127) +#define EXIT_ENOENT NOHUP_FAILURE + + + +#if defined F_GETFD && defined F_SETFD +static inline int set_cloexec_flag (int desc) +{ + int flags = fcntl (desc, F_GETFD, 0); + if (0 <= flags) { + if (flags == (flags |= FD_CLOEXEC) || + fcntl (desc, F_SETFD, flags) != -1) { + return 0; + } + } + return -1; +} +#else +#define set_cloexec_flag(desc) (0) +#endif + +static int fd_reopen (int desired_fd, char const *file, int flags, mode_t mode) +{ + int fd; + + close (desired_fd); + fd = open (file, flags, mode); + if (fd == desired_fd || fd < 0) + return fd; + else { + int fd2 = fcntl (fd, F_DUPFD, desired_fd); + int saved_errno = errno; + close (fd); + errno = saved_errno; + return fd2; + } +} + + +/* Close standard output, exiting with status 'exit_failure' on failure. + If a program writes *anything* to stdout, that program should close + stdout and make sure that it succeeds before exiting. Otherwise, + suppose that you go to the extreme of checking the return status + of every function that does an explicit write to stdout. The last + printf can succeed in writing to the internal stream buffer, and yet + the fclose(stdout) could still fail (due e.g., to a disk full error) + when it tries to write out that buffered data. Thus, you would be + left with an incomplete output file and the offending program would + exit successfully. Even calling fflush is not always sufficient, + since some file systems (NFS and CODA) buffer written/flushed data + until an actual close call. + + Besides, it's wasteful to check the return value from every call + that writes to stdout -- just let the internal stream state record + the failure. That's what the ferror test is checking below. + + It's important to detect such failures and exit nonzero because many + tools (most notably `make' and other build-management systems) depend + on being able to detect failure in other tools via their exit status. */ + +static void close_stdout (void) +{ + int prev_fail = ferror (stdout); + int none_pending = (0 == __fpending (stdout)); + int fclose_fail = fclose (stdout); + + if (prev_fail || fclose_fail) { + /* If ferror returned zero, no data remains to be flushed, and we'd + otherwise fail with EBADF due to a failed fclose, then assume that + it's ok to ignore the fclose failure. That can happen when a + program like cp is invoked like this `cp a b >&-' (i.e., with + stdout closed) and doesn't generate any output (hence no previous + error and nothing to be flushed). */ + if ((fclose_fail ? errno : 0) == EBADF && !prev_fail && none_pending) + return; + + bb_perror_msg_and_die(bb_msg_write_error); + } +} + + +int nohup_main (int argc, char **argv) +{ + int saved_stderr_fd; + + if (argc < 2) + bb_show_usage(); + + bb_default_error_retval = NOHUP_FAILURE; + + atexit (close_stdout); + + /* If standard input is a tty, replace it with /dev/null. + Note that it is deliberately opened for *writing*, + to ensure any read evokes an error. */ + if (isatty (STDIN_FILENO)) + fd_reopen (STDIN_FILENO, "/dev/null", O_WRONLY, 0); + + /* If standard output is a tty, redirect it (appending) to a file. + First try nohup.out, then $HOME/nohup.out. */ + if (isatty (STDOUT_FILENO)) { + char *in_home = NULL; + char const *file = "nohup.out"; + int fd = fd_reopen (STDOUT_FILENO, file, + O_CREAT | O_WRONLY | O_APPEND, S_IRUSR | S_IWUSR); + + if (fd < 0) { + if ((in_home = getenv ("HOME")) != NULL) { + in_home = concat_path_file(in_home, file); + fd = fd_reopen (STDOUT_FILENO, in_home, + O_CREAT | O_WRONLY | O_APPEND, S_IRUSR | S_IWUSR); + } + if (fd < 0) { + bb_perror_msg("failed to open '%s'", file); + if (in_home) + bb_perror_msg("failed to open '%s'",in_home); + exit (NOHUP_FAILURE); + } + file = in_home; + } + + umask (~(S_IRUSR | S_IWUSR)); + bb_error_msg("appending output to '%s'", file); + if (ENABLE_FEATURE_CLEAN_UP) + free (in_home); + } + + /* If standard error is a tty, redirect it to stdout. */ + if (isatty (STDERR_FILENO)) { + /* Save a copy of stderr before redirecting, so we can use the original + if execve fails. It's no big deal if this dup fails. It might + not change anything, and at worst, it'll lead to suppression of + the post-failed-execve diagnostic. */ + saved_stderr_fd = dup (STDERR_FILENO); + + if (0 <= saved_stderr_fd && set_cloexec_flag (saved_stderr_fd) == -1) + bb_perror_msg_and_die("failed to set the copy" + "of stderr to close on exec"); + + if (dup2 (STDOUT_FILENO, STDERR_FILENO) < 0) { + if (errno != EBADF) + bb_perror_msg_and_die("failed to redirect standard error"); + close (STDERR_FILENO); + } + } else + saved_stderr_fd = STDERR_FILENO; + + signal (SIGHUP, SIG_IGN); + + { + char **cmd = argv + 1; + + execvp (*cmd, cmd); + + /* The execve failed. Output a diagnostic to stderr only if: + - stderr was initially redirected to a non-tty, or + - stderr was initially directed to a tty, and we + can dup2 it to point back to that same tty. + In other words, output the diagnostic if possible, but only if + it will go to the original stderr. */ + if (dup2 (saved_stderr_fd, STDERR_FILENO) == STDERR_FILENO) + bb_perror_msg("cannot run command '%s'",*cmd); + + return (errno == ENOENT ? EXIT_ENOENT : EXIT_CANNOT_INVOKE); + } +} + |