C语言 如何使用 apr 从新进程中运行的程序捕获标准输出/标准输出

Question

问题很简单：如何捕获子程序生成的stderr/stdout输出并将其重定向到文件，该子程序在新进程中运行，使用Apache Portable Runtime的apr_proc_create创建。

最终任务是在单独的进程中运行带有一些参数的外部命令(最好，但不是强制性的(，并将其输出重定向到文件。

到目前为止，我已经有以下代码(为清楚起见，删除了检查(：

apr_procattr_t *attr;
apr_proc_t newproc;
const char *progname;
const char *args[100];
// progname and args are populated with data here
apr_procattr_create(&attr, p);
apr_procattr_io_set(attr, APR_CHILD_BLOCK, APR_CHILD_BLOCK, APR_CHILD_BLOCK);
apr_procattr_cmdtype_set(attr, APR_PROGRAM_PATH);
apr_proc_create(&newproc, progname, args, NULL, attr, p);

使用此代码，子进程的输出被抑制(至少我在控制台中看不到它(，但它不会重定向到文件。使用 APR_NO_PIPE 而不是 APR_CHILD_BLOCK 会导致将子项的输出刷新到父 stdout/stderr 中

APR 似乎很少有"食谱"食谱，所以我无法谷歌它。

有什么提示或建议吗？欢迎非 APR 解决方案，只要它们像我发布的代码一样简单明了。

P.S. 运行在 Debian 6(Linux 2.6.32-5-686 (， gcc 4.4.5 上，但我认为这无关紧要。 :)

Answer 1

APR 的测试用例包含许多有用的示例。在您的情况下，您应该查看testproc.c：

版权声明：此代码受APL 2.0保护

/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
static void test_file_redir(abts_case *tc, void *data)
{
    apr_file_t *testout = NULL;
    apr_file_t *testerr = NULL;
    apr_off_t offset;
    apr_status_t rv;
    const char *args[2];
    apr_procattr_t *attr;
    apr_file_t *testfile = NULL;
    apr_size_t length;
    char *buf;
    testfile = NULL;
    rv = apr_file_open(&testfile, "data/stdin",
                       APR_FOPEN_READ | APR_FOPEN_WRITE | APR_FOPEN_CREATE | APR_FOPEN_EXCL,
                       APR_OS_DEFAULT, p);
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
    rv = apr_file_open(&testout, "data/stdout",
                       APR_FOPEN_READ | APR_FOPEN_WRITE | APR_FOPEN_CREATE | APR_FOPEN_EXCL,
                       APR_OS_DEFAULT, p);
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
    rv = apr_file_open(&testerr, "data/stderr",
                       APR_FOPEN_READ | APR_FOPEN_WRITE | APR_FOPEN_CREATE | APR_FOPEN_EXCL,
                       APR_OS_DEFAULT, p);
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
    length = strlen(TESTSTR);
    apr_file_write(testfile, TESTSTR, &length);
    offset = 0;
    rv = apr_file_seek(testfile, APR_SET, &offset);
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
    ABTS_ASSERT(tc, "File position mismatch, expected 0", offset == 0);
    rv = apr_procattr_create(&attr, p);
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
    rv = apr_procattr_child_in_set(attr, testfile, NULL);
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
    rv = apr_procattr_child_out_set(attr, testout, NULL);
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
    rv = apr_procattr_child_err_set(attr, testerr, NULL);
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
    rv = apr_procattr_dir_set(attr, "data");
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
    rv = apr_procattr_cmdtype_set(attr, APR_PROGRAM_ENV);
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
    args[0] = "proc_child";
    args[1] = NULL;
    rv = apr_proc_create(&newproc, proc_child, args, NULL, 
                         attr, p);
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
    rv = apr_proc_wait(&newproc, NULL, NULL, APR_WAIT);
    ABTS_INT_EQUAL(tc, APR_CHILD_DONE, rv);
    offset = 0;
    rv = apr_file_seek(testout, APR_SET, &offset);
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
    length = 256;
    buf = apr_pcalloc(p, length);
    rv = apr_file_read(testout, buf, &length);
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
    ABTS_STR_EQUAL(tc, TESTSTR, buf);

    apr_file_close(testfile);
    apr_file_close(testout);
    apr_file_close(testerr);
    rv = apr_file_remove("data/stdin", p);;
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
    rv = apr_file_remove("data/stdout", p);;
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
    rv = apr_file_remove("data/stderr", p);;
    ABTS_INT_EQUAL(tc, APR_SUCCESS, rv);
}