[Libguestfs] [PATCH 2/6] cmd: add a child-setup callback

Easy way to do pre-exec setup in the child process. --- src/command.c | 22 ++++++++++++++++++++++ src/guestfs-internal.h | 2 ++ 2 files changed, 24 insertions(+) diff --git a/src/command.c b/src/command.c index e26573d..563d0af 100644 --- a/src/command.c +++ b/src/command.c @@ -134,6 +134,10 @@ struct command /* PID of subprocess (if > 0). */ pid_t pid; + + /* Optional child setup callback. */ + cmd_child_callback child_callback; + void *child_callback_data; }; /* Create a new command handle. */ @@ -308,6 +312,19 @@ guestfs___cmd_clear_close_files (struct command *cmd) cmd->close_files = false; } +/* Set a function to be executed in the child, right before the + * execution. Can be used to setup the child, for example changing + * its current directory. + */ +void +guestfs___cmd_set_child_callback (struct command *cmd, + cmd_child_callback child_callback, + void *data) +{ + cmd->child_callback = child_callback; + cmd->child_callback_data = data; +} + /* Finish off the command by either NULL-terminating the argv array or * adding a terminating \0 to the string, or die with an internal * error if no command has been added. @@ -461,6 +478,11 @@ run_command (struct command *cmd, bool get_stdout_fd, bool get_stderr_fd) /* Set the umask for all subcommands to something sensible (RHBZ#610880). */ umask (022); + if (cmd->child_callback) { + if (cmd->child_callback (cmd->g, cmd->child_callback_data) == -1) + _exit (EXIT_FAILURE); + } + /* Run the command. */ switch (cmd->style) { case COMMAND_STYLE_EXECV: diff --git a/src/guestfs-internal.h b/src/guestfs-internal.h index bd5f675..91e3065 100644 --- a/src/guestfs-internal.h +++ b/src/guestfs-internal.h @@ -857,6 +857,7 @@ extern int guestfs___osinfo_map (guestfs_h *g, const struct guestfs_isoinfo *iso /* command.c */ struct command; typedef void (*cmd_stdout_callback) (guestfs_h *g, void *data, const char *line, size_t len); +typedef int (*cmd_child_callback) (guestfs_h *g, void *data); extern struct command *guestfs___new_command (guestfs_h *g); extern void guestfs___cmd_add_arg (struct command *, const char *arg); extern void guestfs___cmd_add_arg_format (struct command *, const char *fs, ...) @@ -870,6 +871,7 @@ extern void guestfs___cmd_set_stdout_callback (struct command *, cmd_stdout_call extern void guestfs___cmd_set_stderr_to_stdout (struct command *); extern void guestfs___cmd_clear_capture_errors (struct command *); extern void guestfs___cmd_clear_close_files (struct command *); +extern void guestfs___cmd_set_child_callback (struct command *, cmd_child_callback child_callback, void *data); extern int guestfs___cmd_run (struct command *); extern int guestfs___cmd_run_async (struct command *, pid_t *pid, int *stdout_fd, int *stderr_fd); extern int guestfs___cmd_wait (struct command *); -- 1.9.3