/* Copyright (C) 2004-2018 J.F.Dockes
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser 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 <string>
#include <vector>
#include <stack>
#include <sys/types.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
* into 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. Our vfork usage is multithread-compatible as
// far as I can see, but just in case...
static void useVfork(bool 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);
/**
* Try to set a limit on child process vm size. This will use
* setrlimit() and RLIMIT_AS/VMEM if available. Parameter is in
* units of 2**10. Must be called before starting the command, default
* is inherit from parent.
*/
void setrlimit_as(int mbytes);
/**
* Set function objects to call whenever new data is available or on
* select timeout. The data itself is stored in the output string.
* Must be set before calling doexec.
*/
void setAdvise(ExecCmdAdvise *adv);
/*
* Set function object to call whenever new data is needed. The
* data should be stored in the input string. Must be set before
* calling doexec()
*/
void setProvide(ExecCmdProvide *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 advise routine (which normally checks for cancellation).
*/
void setTimeout(int 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);
/**
* Set kill wait timeout. This is the maximum time we'll wait for
* the command after sending a SIGTERM, before sending a SIGKILL.
* @param mS the maximum number of mS to wait. Note that values
* below 1000 mS make no sense as the program will sleep for
* longer time before retrying the waitpid(). Use -1 for
* forever (bad idea), 0 for absolutely no pity.
*/
void setKillTimeout(int mS);
/**
* 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 output 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);
/** Same as doexec but cmd and args in one vector */
int doexec1(const std::vector<std::string>& args,
const std::string *input = 0,
std::string *output = 0) {
if (args.empty()) {
return -1;
}
return doexec(args[0],
std::vector<std::string>(args.begin() + 1, args.end()),
input, output);
}
/*
* 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);
/** Read line. Will call back periodically to check for cancellation */
int getline(std::string& data);
/** Read line. Timeout after timeosecs seconds */
int getline(std::string& data, int timeosecs);
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();
/**
* 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. In the owner thread, any I/O loop
* will exit at the next iteration, and the process will be waited for.
*/
void setKill();
/**
* Get rid of current process (become ready for start). This will signal
* politely the process to stop, wait a moment, then terminate it. This
* is a blocking call.
*/
void zapChild();
/**
* Request process termination (SIGTERM or equivalent). This returns
* immediately
*/
bool requestChildExit();
enum ExFlags {EXF_NONE,
// Only does anything on windows. Used when starting
// a viewer. The default is to hide the window,
// because it avoids windows appearing and
// disappearing when executing stuff for previewing
EXF_SHOWWINDOW = 1,
// Windows only: show maximized
EXF_MAXIMIZED = 2,
};
ExecCmd(int flags = 0);
~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);
class Internal;
private:
Internal *m;
/* Copyconst and assignment are 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_ */