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process-util: add new safe_fork() flag for connecting stdout to stderr

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This adds a new safe_fork() flag. If set the child process' fd 1 becomes
fd 2 of the caller. This is useful for invoking tools (such as various
mkfs/fsck implementations) that output status messages to stdout, but
which we invoke and don't want to pollute stdout with their output.
This commit is contained in:
Lennart Poettering
2019-12-04 10:59:42 +01:00
parent 7a509acc29
commit 8987afc4d1
2 changed files with 18 additions and 10 deletions
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src/basic/process-util.c
+7
View File
@@ -1337,6 +1337,13 @@ int safe_fork_full(
log_full_errno(prio, r, "Failed to connect stdin/stdout to /dev/null: %m");
_exit(EXIT_FAILURE);
}
} else if (flags & FORK_STDOUT_TO_STDERR) {
if (dup2(STDERR_FILENO, STDOUT_FILENO) < 0) {
log_full_errno(prio, r, "Failed to connect stdout to stderr: %m");
_exit(EXIT_FAILURE);
}
}
if (flags & FORK_RLIMIT_NOFILE_SAFE) {
src/basic/process-util.h
+11 -10
View File
@@ -147,16 +147,17 @@ void reset_cached_pid(void);
int must_be_root(void);
typedef enum ForkFlags {
FORK_RESET_SIGNALS = 1 << 0, /* Reset all signal handlers and signal mask */
FORK_CLOSE_ALL_FDS = 1 << 1, /* Close all open file descriptors in the child, except for 0,1,2 */
FORK_DEATHSIG = 1 << 2, /* Set PR_DEATHSIG in the child */
FORK_NULL_STDIO = 1 << 3, /* Connect 0,1,2 to /dev/null */
FORK_REOPEN_LOG = 1 << 4, /* Reopen log connection */
FORK_LOG = 1 << 5, /* Log above LOG_DEBUG log level about failures */
FORK_WAIT = 1 << 6, /* Wait until child exited */
FORK_NEW_MOUNTNS = 1 << 7, /* Run child in its own mount namespace */
FORK_MOUNTNS_SLAVE = 1 << 8, /* Make child's mount namespace MS_SLAVE */
FORK_RLIMIT_NOFILE_SAFE = 1 << 9, /* Set RLIMIT_NOFILE soft limit to 1K for select() compat */
FORK_RESET_SIGNALS = 1 << 0, /* Reset all signal handlers and signal mask */
FORK_CLOSE_ALL_FDS = 1 << 1, /* Close all open file descriptors in the child, except for 0,1,2 */
FORK_DEATHSIG = 1 << 2, /* Set PR_DEATHSIG in the child */
FORK_NULL_STDIO = 1 << 3, /* Connect 0,1,2 to /dev/null */
FORK_REOPEN_LOG = 1 << 4, /* Reopen log connection */
FORK_LOG = 1 << 5, /* Log above LOG_DEBUG log level about failures */
FORK_WAIT = 1 << 6, /* Wait until child exited */
FORK_NEW_MOUNTNS = 1 << 7, /* Run child in its own mount namespace */
FORK_MOUNTNS_SLAVE = 1 << 8, /* Make child's mount namespace MS_SLAVE */
FORK_RLIMIT_NOFILE_SAFE = 1 << 9, /* Set RLIMIT_NOFILE soft limit to 1K for select() compat */
FORK_STDOUT_TO_STDERR = 1 << 10, /* Make stdout a copy of stderr */
} ForkFlags;
int safe_fork_full(const char *name, const int except_fds[], size_t n_except_fds, ForkFlags flags, pid_t *ret_pid);