ClickHouse/dbms/Common/ShellCommand.h

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#pragma once
#include <memory>
#include <IO/ReadBufferFromFile.h>
#include <IO/WriteBufferFromFile.h>
namespace DB
{
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/** Lets you run the command,
* read it stdout and stderr; write to stdin;
* wait for completion.
*
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* The implementation is similar to the popen function from POSIX (see libc source code).
*
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* The most important difference: uses vfork instead of fork.
* This is done because fork does not work (with a memory shortage error),
* with some overcommit settings, if the address space of the process is more than half the amount of available memory.
* Also, changing memory maps - a fairly resource-intensive operation.
*
* The second difference - allows to work simultaneously with stdin, and with stdout, and with stderr of running process,
* and also to obtain the return code and completion status.
*/
class ShellCommand
{
private:
pid_t pid;
bool wait_called = false;
bool terminate_in_destructor;
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ShellCommand(pid_t pid_, int in_fd_, int out_fd_, int err_fd_, bool terminate_in_destructor_);
static Poco::Logger * getLogger();
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/// Print command name and the list of arguments to log. NOTE: No escaping of arguments is performed.
static void logCommand(const char * filename, char * const argv[]);
static std::unique_ptr<ShellCommand> executeImpl(const char * filename, char * const argv[], bool pipe_stdin_only, bool terminate_in_destructor);
public:
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WriteBufferFromFile in; /// If the command reads from stdin, do not forget to call in.close() after writing all the data there.
ReadBufferFromFile out;
ReadBufferFromFile err;
~ShellCommand();
/// Run the command using /bin/sh -c.
/// If terminate_in_destructor is true, send terminate signal in destructor and don't wait process.
static std::unique_ptr<ShellCommand> execute(const std::string & command, bool pipe_stdin_only = false, bool terminate_in_destructor = false);
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/// Run the executable with the specified arguments. `arguments` - without argv[0].
/// If terminate_in_destructor is true, send terminate signal in destructor and don't wait process.
static std::unique_ptr<ShellCommand> executeDirect(const std::string & path, const std::vector<std::string> & arguments, bool terminate_in_destructor = false);
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/// Wait for the process to end, throw an exception if the code is not 0 or if the process was not completed by itself.
void wait();
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/// Wait for the process to finish, see the return code. To throw an exception if the process was not completed independently.
int tryWait();
};
}