/** * apr tutorial sample code * http://dev.ariel-networks.com/apr/ */#ifdef HAVE_CONFIG_H#include <config.h>#endif#include <stdio.h>#include <stdlib.h>#include <assert.h>#include <apr_general.h>#include <apr_thread_proc.h>#include <apr_strings.h>/** * Parse the output and find the largest file size. */#define EXEC_CMD	"/bin/ls"#define EXEC_CMD_ARG	"-l"/* default buffer size */#define BUFSIZE			4096/* useful macros */#undef MAX#define MAX(a, b)  (((a) > (b)) ? (a) : (b))/** * The max number of child process arguments. Normally, 64 is enough. */#define APP_MAX_ARGC	64static apr_status_t read_pipe(const apr_procattr_t *pattr, apr_pool_t *mp){    apr_status_t rv;    int argc = 0;    const char* argv[APP_MAX_ARGC];    apr_proc_t proc;    apr_size_t max_sz = 0;    int is_firstline = TRUE;    argv[argc++] = EXEC_CMD;    argv[argc++] = EXEC_CMD_ARG;    argv[argc++] = NULL;/* @argvs should be null-terminated */    if ((rv = apr_proc_create(&proc, EXEC_CMD, (const char* const*)argv,                              NULL, (apr_procattr_t*)pattr, mp)) != APR_SUCCESS) {        return rv;    }    while (1) {        char buf[BUFSIZE];        char **tokens;        /* read the command's output through the pipe */        rv = apr_file_gets(buf, sizeof(buf), proc.out);        if (APR_STATUS_IS_EOF(rv)) {            break;        }        if (is_firstline) {/* skip the first line */            is_firstline = FALSE;            continue;        }        apr_tokenize_to_argv(buf, &tokens, mp);        assert(tokens[4]);        max_sz = MAX(max_sz, atoi(tokens[4]));    }    apr_file_close(proc.out);    printf("the largest file size is %" APR_SIZE_T_FMT "\n", max_sz);            {        int st;        apr_exit_why_e why;                    rv = apr_proc_wait(&proc, &st, &why, APR_WAIT);        if (APR_STATUS_IS_CHILD_DONE(rv)) {            printf("child done: why = %d, exit status = %d\n", why, st);        } else {            printf("child notdone\n");        }    }    return APR_SUCCESS;}/** * process execution and communicate through the pipe sample code * @remark Error checks omitted */int main(int argc, const char *argv[]){    apr_status_t rv;    apr_pool_t *mp;    apr_procattr_t *pattr;            apr_initialize();    apr_pool_create(&mp, NULL);    /* prepare process attribute */    if ((rv = apr_procattr_create(&pattr, mp)) != APR_SUCCESS) {        goto error;    }    if ((rv = apr_procattr_io_set(pattr, APR_NO_PIPE, APR_FULL_BLOCK, APR_NO_PIPE)) != APR_SUCCESS) {        goto error;    }    /* default value: APR_PROGRAM */    if ((rv = apr_procattr_cmdtype_set(pattr, APR_PROGRAM_ENV)) != APR_SUCCESS) {        goto error;    }    /* run the program and read the output from the pipe */    read_pipe(pattr, mp);    apr_terminate();    return 0; error:    {        char errbuf[256];        apr_strerror(rv, errbuf, sizeof(errbuf));        printf("error: %d, %s\n", rv, errbuf);    }    apr_terminate();    return -1;}