C++調用其它應用並取得輸出結果

函數說明

#include <stdio.h>

FILE* popen(const char* command , const char* type);
int pclose(FILE* stream);

　　popen()函數通過創建一個管道，調用fork()產生一個子進程，執行一個shell以運行命令來開啟一個進程。pclose()函數關閉標准I/O流，等待命令執行結束，然后返回shell的終止狀態。如果shell不能被執行，則pclose()返回的終止狀態與shell已執行exit一樣。

　　type參數只能是讀或者寫中的一種，得到的返回值（標准I/O流）也具有和type相應的只讀或只寫類型。如果type是"r"則文件指針連接到command的標准輸出；如果type是"w"則文件指針連接到command的標准輸入。(在windows中支持"b")

　　command參數是一個指向以NULL結束的shell命令字符串的指針。這行命令將被傳到bin/sh並使用-c標志，shell將執行這個命令。

　　popen()的返回值是個標准I/O流，必須由pclose來終止。前面提到這個流是單向的（只能用於讀或寫）。向這個流寫內容相當於寫入該命令的標准輸入，命令的標准輸出和調用popen()的進程相同；與之相反的，從流中讀數據相當於讀取命令的標准輸出，命令的標准輸入和調用popen()的進程相同。

　　如果調用fork()或pipe()失敗，或者不能分配內存將返回NULL，否則返回標准I/O流。popen()沒有為內存分配失敗設置errno值。如果調用fork()或pipe()時出現錯誤，errno被設為相應的錯誤類型。如果type參數不合法，errno將返回EINVAL。

 代碼

#include <cstdio>
#include <string>
#include <cstring>

#if __linux__
#define __FILENAME__ (strrchr("/" __FILE__, '/') + 1)
#else
#define __FILENAME__ (strrchr("\\" __FILE__, '\\') + 1)
#endif
#define LOGI(fmt, ...) printf("[%s] %s:%d " fmt "\n", __func__, __FILENAME__, __LINE__, ##__VA_ARGS__)


std::string ExecCmd(const std::string& strCmd, const std::string& strMode = "r")
{
    FILE* fp = ::popen(strCmd.c_str(), strMode.c_str());
    if (!fp)
    {
        LOGI("open cmd<%s> failed. errno:%d, %s", strCmd.c_str(), errno, strerror(errno));
        return "";
    }

    std::string strResult;
    char szbuffer[1024 * 10]{};
    while (!::feof(fp))
    {
        size_t iCnt = ::fread(szbuffer, 1, sizeof(szbuffer), fp);
        if (iCnt > 0)
        {
            strResult.append(szbuffer, szbuffer + iCnt);
        }
    }

    ::pclose(fp);
    return strResult;
}

 

調用

int main()
{
#if __linux__
    std::string strResult = ExecCmd(R"(ifconfig)");
#else
    std::string strResult = ExecCmd(R"(ipconfig)", "rb");
#endif
    if (!strResult.empty())
    {
        int iCnt = strResult.length();
        LOGI("len:%d\n%s", iCnt, strResult.data());
    }
}

 

二進制模式

當被調用的應用程序返回的數據非文本, 而是二進制數據, 則popen傳入的模式需要加入標志"b", 才能正確的讀取到數據. 如下例所示的 test 文件是一個二進制數據文件, 當以 "r" 模式打開會少若干字節.

readfile.py

import os
import sys


def main():
    # sys.argv.append(sys.argv[0])
    filename = sys.argv[1] if len(sys.argv) > 1 else ""
    with open(filename, "rb") as fp:
        byte_data = fp.read()
        sys.stdout.buffer.write(byte_data)


if __name__ == '__main__':
    main()

int main()
{
　　// 錯誤的模式
    std::string strResult = ExecCmd(R"(python D:\UserData\pycharm\study\util\readfile.py test)", "r");
    if (!strResult.empty())
    {
        int iCnt = strResult.length();
        LOGI("len:%d(%d)\n%s", iCnt, strlen(strResult.data()), strResult.data());
    }
}

運行結果:

 

 test 文件在 notepad++ 中打開后如下所示(其真實大小為309字節):

 

 

 

錯誤碼

#include <stdio.h>
const char* strerror(int errno);

 錯誤碼定義

// errno-base.h

#ifndef _ASM_GENERIC_ERRNO_BASE_H
#define _ASM_GENERIC_ERRNO_BASE_H

#define EPERM 1 /* Operation not permitted */
#define ENOENT 2 /* No such file or directory */
#define ESRCH 3 /* No such process */
#define EINTR 4 /* Interrupted system call */
#define EIO 5 /* I/O error */
#define ENXIO 6 /* No such device or address */
#define E2BIG 7 /* Argument list too long */
#define ENOEXEC 8 /* Exec format error */
#define EBADF 9 /* Bad file number */
#define ECHILD 10 /* No child processes */
#define EAGAIN 11 /* Try again */
#define ENOMEM 12 /* Out of memory */
#define EACCES 13 /* Permission denied */
#define EFAULT 14 /* Bad address */
#define ENOTBLK 15 /* Block device required */
#define EBUSY 16 /* Device or resource busy */
#define EEXIST 17 /* File exists */
#define EXDEV 18 /* Cross-device link */
#define ENODEV 19 /* No such device */
#define ENOTDIR 20 /* Not a directory */
#define EISDIR 21 /* Is a directory */
#define EINVAL 22 /* Invalid argument */
#define ENFILE 23 /* File table overflow */
#define EMFILE 24 /* Too many open files */
#define ENOTTY 25 /* Not a typewriter */
#define ETXTBSY 26 /* Text file busy */
#define EFBIG 27 /* File too large */
#define ENOSPC 28 /* No space left on device */
#define ESPIPE 29 /* Illegal seek */
#define EROFS 30 /* Read-only file system */
#define EMLINK 31 /* Too many links */
#define EPIPE 32 /* Broken pipe */
#define EDOM 33 /* Math argument out of domain of func */
#define ERANGE 34 /* Math result not representable */

#endif

 

 

 

// errno.h

#ifndef _ASM_GENERIC_ERRNO_H
#define _ASM_GENERIC_ERRNO_H

#include <asm-generic/errno-base.h>

#define EDEADLK 35 /* Resource deadlock would occur */
#define ENAMETOOLONG 36 /* File name too long */
#define ENOLCK 37 /* No record locks available */
#define ENOSYS 38 /* Function not implemented */
#define ENOTEMPTY 39 /* Directory not empty */
#define ELOOP 40 /* Too many symbolic links encountered */
#define EWOULDBLOCK EAGAIN /* Operation would block */
#define ENOMSG 42 /* No message of desired type */
#define EIDRM 43 /* Identifier removed */
#define ECHRNG 44 /* Channel number out of range */
#define EL2NSYNC 45 /* Level 2 not synchronized */
#define EL3HLT 46 /* Level 3 halted */
#define EL3RST 47 /* Level 3 reset */
#define ELNRNG 48 /* Link number out of range */
#define EUNATCH 49 /* Protocol driver not attached */
#define ENOCSI 50 /* No CSI structure available */
#define EL2HLT 51 /* Level 2 halted */
#define EBADE 52 /* Invalid exchange */
#define EBADR 53 /* Invalid request descriptor */
#define EXFULL 54 /* Exchange full */
#define ENOANO 55 /* No anode */
#define EBADRQC 56 /* Invalid request code */
#define EBADSLT 57 /* Invalid slot */

#define EDEADLOCK EDEADLK

#define EBFONT 59 /* Bad font file format */
#define ENOSTR 60 /* Device not a stream */
#define ENODATA 61 /* No data available */
#define ETIME 62 /* Timer expired */
#define ENOSR 63 /* Out of streams resources */
#define ENONET 64 /* Machine is not on the network */
#define ENOPKG 65 /* Package not installed */
#define EREMOTE 66 /* Object is remote */
#define ENOLINK 67 /* Link has been severed */
#define EADV 68 /* Advertise error */
#define ESRMNT 69 /* Srmount error */
#define ECOMM 70 /* Communication error on send */
#define EPROTO 71 /* Protocol error */
#define EMULTIHOP 72 /* Multihop attempted */
#define EDOTDOT 73 /* RFS specific error */
#define EBADMSG 74 /* Not a data message */
#define EOVERFLOW 75 /* Value too large for defined data type */
#define ENOTUNIQ 76 /* Name not unique on network */
#define EBADFD 77 /* File descriptor in bad state */
#define EREMCHG 78 /* Remote address changed */
#define ELIBACC 79 /* Can not access a needed shared library */
#define ELIBBAD 80 /* Accessing a corrupted shared library */
#define ELIBSCN 81 /* .lib section in a.out corrupted */
#define ELIBMAX 82 /* Attempting to link in too many shared libraries */
#define ELIBEXEC 83 /* Cannot exec a shared library directly */
#define EILSEQ 84 /* Illegal byte sequence */
#define ERESTART 85 /* Interrupted system call should be restarted */
#define ESTRPIPE 86 /* Streams pipe error */
#define EUSERS 87 /* Too many users */
#define ENOTSOCK 88 /* Socket operation on non-socket */
#define EDESTADDRREQ 89 /* Destination address required */
#define EMSGSIZE 90 /* Message too long */
#define EPROTOTYPE 91 /* Protocol wrong type for socket */
#define ENOPROTOOPT 92 /* Protocol not available */
#define EPROTONOSUPPORT 93 /* Protocol not supported */
#define ESOCKTNOSUPPORT 94 /* Socket type not supported */
#define EOPNOTSUPP 95 /* Operation not supported on transport endpoint */
#define EPFNOSUPPORT 96 /* Protocol family not supported */
#define EAFNOSUPPORT 97 /* Address family not supported by protocol */
#define EADDRINUSE 98 /* Address already in use */
#define EADDRNOTAVAIL 99 /* Cannot assign requested address */
#define ENETDOWN 100 /* Network is down */
#define ENETUNREACH 101 /* Network is unreachable */
#define ENETRESET 102 /* Network dropped connection because of reset */
#define ECONNABORTED 103 /* Software caused connection abort */
#define ECONNRESET 104 /* Connection reset by peer */
#define ENOBUFS 105 /* No buffer space available */
#define EISCONN 106 /* Transport endpoint is already connected */
#define ENOTCONN 107 /* Transport endpoint is not connected */
#define ESHUTDOWN 108 /* Cannot send after transport endpoint shutdown */
#define ETOOMANYREFS 109 /* Too many references: cannot splice */
#define ETIMEDOUT 110 /* Connection timed out */
#define ECONNREFUSED 111 /* Connection refused */
#define EHOSTDOWN 112 /* Host is down */
#define EHOSTUNREACH 113 /* No route to host */
#define EALREADY 114 /* Operation already in progress */
#define EINPROGRESS 115 /* Operation now in progress */
#define ESTALE 116 /* Stale file handle */
#define EUCLEAN 117 /* Structure needs cleaning */
#define ENOTNAM 118 /* Not a XENIX named type file */
#define ENAVAIL 119 /* No XENIX semaphores available */
#define EISNAM 120 /* Is a named type file */
#define EREMOTEIO 121 /* Remote I/O error */
#define EDQUOT 122 /* Quota exceeded */

#define ENOMEDIUM 123 /* No medium found */
#define EMEDIUMTYPE 124 /* Wrong medium type */
#define ECANCELED 125 /* Operation Canceled */
#define ENOKEY 126 /* Required key not available */
#define EKEYEXPIRED 127 /* Key has expired */
#define EKEYREVOKED 128 /* Key has been revoked */
#define EKEYREJECTED 129 /* Key was rejected by service */

/* for robust mutexes */
#define EOWNERDEAD 130 /* Owner died */
#define ENOTRECOVERABLE 131 /* State not recoverable */

#define ERFKILL 132 /* Operation not possible due to RF-kill */

#define EHWPOISON 133 /* Memory page has hardware error */

#endif