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59 lines
2.0 KiB
C++
59 lines
2.0 KiB
C++
#pragma once
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#include <memory>
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#include <IO/ReadBufferFromFile.h>
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#include <IO/WriteBufferFromFile.h>
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namespace DB
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{
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/** Lets you run the command,
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* read it stdout and stderr; write to stdin;
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* wait for completion.
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*
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* The implementation is similar to the popen function from POSIX (see libc source code).
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*
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* The most important difference: uses vfork instead of fork.
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* This is done because fork does not work (with a memory shortage error),
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* with some overcommit settings, if the address space of the process is more than half the amount of available memory.
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* Also, changing memory maps - a fairly resource-intensive operation.
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*
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* The second difference - allows to work simultaneously with stdin, and with stdout, and with stderr of running process,
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* and also to obtain the return code and completion status.
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*/
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class ShellCommand
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{
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private:
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pid_t pid;
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bool wait_called = false;
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ShellCommand(pid_t pid, int in_fd, int out_fd, int err_fd)
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: pid(pid), in(in_fd), out(out_fd), err(err_fd) {}
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static std::unique_ptr<ShellCommand> executeImpl(const char * filename, char * const argv[], bool pipe_stdin_only);
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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.
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ReadBufferFromFile out;
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ReadBufferFromFile err;
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~ShellCommand();
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/// Run the command using /bin/sh -c
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static std::unique_ptr<ShellCommand> execute(const std::string & command, bool pipe_stdin_only = false);
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/// Run the executable with the specified arguments. `arguments` - without argv[0].
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static std::unique_ptr<ShellCommand> executeDirect(const std::string & path, const std::vector<std::string> & arguments);
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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.
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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.
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int tryWait();
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};
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}
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