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How to capture stdout / stderr output from a program running in a new process using apr?

The question is quite simple: how can I capture and redirect the output of stderr / stdout, created by a child program, launched in a new process, created using Apache Portable Runtime to a file apr_proc_create.

The ultimate goal is to run an external command with some arguments in a separate process (desirable, but not necessary) and redirect the output to a file.

So far I have the following code (remote checks for clarity):

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);

Using this code, the output of the child process is suppressed (at least I don’t see it in the console), but it is not redirected to the file. Using APR_NO_PIPEinstead APR_CHILD_BLOCKremoves the child output to the parent stdout / stderr

APR, -, , .

? , APR, , , , .

P.S. Debian 6 (Linux 2.6.32-5-686), gcc 4.4.5, , .:)

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1

APR . testproc.c:

: APL 2.0

/* 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);
}
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