fish-shell/src/exec.h

// Prototypes for functions for executing a program.
#ifndef FISH_EXEC_H
#define FISH_EXEC_H

#include <stddef.h>

#include <vector>

#include "common.h"

/// Pipe redirection error message.
#define PIPE_ERROR _(L"An error occurred while setting up pipe")

/// Execute the processes specified by j.
///
/// I've put a fair bit of work into making builtins behave like other programs as far as pipes are
/// concerned. Unlike i.e. bash, builtins can pipe to other builtins with arbitrary amounts of data,
/// and so on. To do this, after a builtin is run in the real process, it forks and a dummy process
/// is created, responsible for writing the output of the builtin. This is surprisingly cheap on my
/// computer, probably because of the marvels of copy on write forking.
///
/// This rule is short circuited in the case where a builtin does not output to a pipe and does in
/// fact not output anything. The speed improvement from this optimization is not noticable on a
/// normal computer/OS in regular use, but the promiscous amounts of forking that resulted was
/// responsible for a huge slowdown when using Valgrind as well as when doing complex
/// command-specific completions.
class job_t;
class parser_t;
void exec_job(parser_t &parser, job_t *j);

/// Evaluate the expression cmd in a subshell, add the outputs into the list l. On return, the
/// status flag as returned bu \c proc_gfet_last_status will not be changed.
///
/// \param cmd the command to execute
/// \param outputs The list to insert output into.
///
/// \return the status of the last job to exit, or -1 if en error was encountered.
int exec_subshell(const wcstring &cmd, std::vector<wcstring> &outputs, bool preserve_exit_status,
                  bool is_subcmd = false);
int exec_subshell(const wcstring &cmd, bool preserve_exit_status, bool is_subcmd = false);

/// Loops over close until the syscall was run without being interrupted.
void exec_close(int fd);

/// Call pipe(), and add resulting fds to open_fds, the list of opened file descriptors for pipes.
/// The pipes are marked CLO_EXEC.
int exec_pipe(int fd[2]);

/// Gets the interpreter for a given command.
char *get_interpreter(const char *command, char *interpreter, size_t buff_size);

#endif