/* Copyright (C) 2004 J.F.Dockes
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the
* Free Software Foundation, Inc.,
* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#ifndef _EXECMD_H_INCLUDED_
#define _EXECMD_H_INCLUDED_
#include <signal.h>
#include <string>
#include <vector>
#include <stack>
#include "netcon.h"
/**
* Callback function object to advise of new data arrival, or just periodic
* heartbeat if cnt is 0.
*
* To interrupt the command, the code using ExecCmd should either
* raise an exception inside newData() (and catch it in doexec's caller), or
* call ExecCmd::setKill()
*
*/
class ExecCmdAdvise {
public:
virtual ~ExecCmdAdvise() {}
virtual void newData(int cnt) = 0;
};
/**
* Callback function object to get more input data. Data has to be provided
* in the initial input string, set it to empty to signify eof.
*/
class ExecCmdProvide {
public:
virtual ~ExecCmdProvide() {}
virtual void newData() = 0;
};
/**
* Execute command possibly taking both input and output (will do
* asynchronous io as appropriate for things to work).
*
* Input to the command can be provided either once in a parameter to doexec
* or provided in chunks by setting a callback which will be called to
* request new data. In this case, the 'input' parameter to doexec may be
* empty (but not null)
*
* Output from the command is normally returned in a single string, but a
* callback can be set to be called whenever new data arrives, in which case
* it is permissible to consume the data and erase the string.
*
* Note that SIGPIPE should be ignored and SIGCLD blocked when calling doexec,
* else things might fail randomly. (This is not done inside the class because
* of concerns with multithreaded programs).
*
*/
class ExecCmd {
public:
// Use vfork instead of fork. This must not be called in a multithreaded
// program.
static void useVfork(bool on)
{
o_useVfork = on;
}
/**
* Add/replace environment variable before executing command. This must
* be called before doexec() to have an effect (possibly multiple
* times for several variables).
* @param envassign an environment assignment string ("name=value")
*/
void putenv(const std::string &envassign);
void putenv(const std::string &name, const std::string& value);
/**
* Set function objects to call whenever new data is available or on
* select timeout / whenever new data is needed to send. Must be called
* before doexec()
*/
void setAdvise(ExecCmdAdvise *adv) {m_advise = adv;}
void setProvide(ExecCmdProvide *p) {m_provide = p;}
/**
* Set select timeout in milliseconds. The default is 1 S.
* This is NOT a time after which an error will occur, but the period of
* the calls to the cancellation check routine.
*/
void setTimeout(int mS) {if (mS > 30) m_timeoutMs = mS;}
/**
* Set destination for stderr data. The default is to let it alone (will
* usually go to the terminal or to wherever the desktop messages go).
* There is currently no option to put stderr data into a program variable
* If the parameter can't be opened for writing, the command's
* stderr will be closed.
*/
void setStderr(const std::string &stderrFile) {m_stderrFile = stderrFile;}
/**
* Execute command.
*
* Both input and output can be specified, and asynchronous
* io (select-based) is used to prevent blocking. This will not
* work if input and output need to be synchronized (ie: Q/A), but
* works ok for filtering.
* The function is exception-safe. In case an exception occurs in the
* advise callback, fds and pids will be cleaned-up properly.
*
* @param cmd the program to execute. This must be an absolute file name
* or exist in the PATH.
* @param args the argument vector (NOT including argv[0]).
* @param input Input to send TO the command.
* @param output Output FROM the command.
* @return the exec ouput status (0 if ok), or -1
*/
int doexec(const std::string &cmd, const std::vector<std::string>& args,
const std::string *input = 0,
std::string *output = 0);
/*
* The next four methods can be used when a Q/A dialog needs to be
* performed with the command
*/
int startExec(const std::string &cmd, const std::vector<std::string>& args,
bool has_input, bool has_output);
int send(const std::string& data);
int receive(std::string& data, int cnt = -1);
int getline(std::string& data);
int wait();
/** Wait with WNOHANG set.
@return true if process exited, false else.
@param O: status, the wait(2) call's status value */
bool maybereap(int *status);
pid_t getChildPid() {return m_pid;}
/**
* Cancel/kill command. This can be called from another thread or
* from the advise callback, which could also raise an exception to
* accomplish the same thing
*/
void setKill() {m_killRequest = true;}
/**
* Get rid of current process (become ready for start).
*/
void zapChild() {setKill(); (void)wait();}
ExecCmd()
: m_advise(0), m_provide(0), m_timeoutMs(1000)
{
reset();
}
~ExecCmd();
/**
* Utility routine: check if/where a command is found according to the
* current PATH (or the specified one
* @param cmd command name
* @param exe on return, executable path name if found
* @param path exec seach path to use instead of getenv(PATH)
* @return true if found
*/
static bool which(const std::string& cmd, std::string& exe, const char* path = 0);
/**
* Execute command and return stdout output in a string
* @param cmd input: command and args
* @param out output: what the command printed
* @return true if exec status was 0
*/
static bool backtick(const std::vector<std::string> cmd, std::string& out);
friend class ExecCmdRsrc;
private:
static bool o_useVfork;
std::vector<std::string> m_env;
ExecCmdAdvise *m_advise;
ExecCmdProvide *m_provide;
bool m_killRequest;
int m_timeoutMs;
std::string m_stderrFile;
// Pipe for data going to the command
int m_pipein[2];
NetconP m_tocmd;
// Pipe for data coming out
int m_pipeout[2];
NetconP m_fromcmd;
// Subprocess id
pid_t m_pid;
// Saved sigmask
sigset_t m_blkcld;
// Reset internal state indicators. Any resources should have been
// previously freed
void reset() {
m_killRequest = false;
m_pipein[0] = m_pipein[1] = m_pipeout[0] = m_pipeout[1] = -1;
m_pid = -1;
sigemptyset(&m_blkcld);
}
// Child process code
inline void dochild(const std::string &cmd, const char **argv,
const char **envv, bool has_input, bool has_output);
/* Copyconst and assignment private and forbidden */
ExecCmd(const ExecCmd &) {}
ExecCmd& operator=(const ExecCmd &) {return *this;};
};
/**
* Rexecute self process with the same arguments.
*
* Note that there are some limitations:
* - argv[0] has to be valid: an executable name which will be found in
* the path when exec is called in the initial working directory. This is
* by no means guaranteed. The shells do this, but argv[0] could be an
* arbitrary string.
* - The initial working directory must be found and remain valid.
* - We don't try to do anything with fd 0,1,2. If they were changed by the
* program, their initial meaning won't be the same as at the moment of the
* initial invocation.
* - We don't restore the signals. Signals set to be blocked
* or ignored by the program will remain ignored even if this was not their
* initial state.
* - The environment is also not restored.
* - Others system aspects ?
* - Other program state: application-dependant. Any external cleanup
* (temp files etc.) must be performed by the application. ReExec()
* duplicates the atexit() function to make this easier, but the
* ReExec().atexit() calls must be done explicitely, this is not automatic
*
* In short, this is usable in reasonably controlled situations and if there
* are no security issues involved, but this does not perform miracles.
*/
class ReExec {
public:
ReExec() {}
ReExec(int argc, char *argv[]);
void init(int argc, char *argv[]);
int atexit(void (*function)(void))
{
m_atexitfuncs.push(function);
return 0;
}
void reexec();
const std::string& getreason() {return m_reason;}
// Insert new args into the initial argv. idx designates the place
// before which the new args are inserted (the default of 1
// inserts after argv[0] which would probably be an appropriate
// place for additional options)
void insertArgs(const std::vector<std::string>& args, int idx = 1);
void removeArg(const std::string& arg);
private:
std::vector<std::string> m_argv;
std::string m_curdir;
int m_cfd;
std::string m_reason;
std::stack<void (*)(void)> m_atexitfuncs;
};
#endif /* _EXECMD_H_INCLUDED_ */