【发布时间】：2016-03-15 19:38:48
【问题描述】：
我尝试使用fork() 进入文件夹并读取文件。我使用file tree walk 函数递归地进入文件夹。基本思想是在一个目录中会有多个子文件和目录。孩子们分别和同时阅读每个文件。但是，如果有目录，则子级将成为读取文件的子级的父级。
static int soner_each_time(const char *filepath, const struct stat *info,
int typeflag, struct FTW *ftwinfo)
{
pid_t pid = 0;
char buf[BUFSIZE];
int status;
int i = 0;
/* The variables are related to functions of reading file */
int totalLines;
char arr[TOTALNUMBEROFLINES][BUFSIZE];
int retval;
const char *const filename = filepath + ftwinfo->base;
if (( pid = fork()) < 0) {
const int cause = errno;
fprintf(stderr, "Fork error: %s\n", strerror(cause));
errno = cause;
return -1;
}
else if( pid > 0 ) // parent
{
if (typeflag == FTW_DP || typeflag == FTW_D)
{
sprintf(buf, "%*s%s\n\n", ftwinfo->level * 4, "", filepath);
write(1, buf, strlen(buf));
pid = wait(&status);
if (pid == -1)
perror("Failed to wait for child");
else if (WIFEXITED(status) && !WEXITSTATUS(status))
printf("parent [%d] reaped child [%d]\n", getpid(), pid);
else if (WIFEXITED(status))
printf("Child %ld terminated with return status %d\n",
(long)pid, WEXITSTATUS(status));
else if (WIFSIGNALED(status))
printf("Child %ld terminated due to uncaught signal %d\n",
(long)pid, WTERMSIG(status));
else if (WIFSTOPPED(status))
printf("Child %ld stopped due to signal %d\n",
(long)pid, WSTOPSIG(status));
}
}
if (pid == 0) // child
{
if (typeflag == FTW_F)
{
sprintf(buf, "||| Child [%d] of parent [%d]: %s |||\n", getpid(), getppid(), filename);
write(1, buf, strlen(buf));
/* Both of them are about reading function */
totalLines = storeLinesInArray(filename, arr);
retval = for_each_file(filename, totalLines, key, arr);
sprintf(buf, "||| Child [%d] of parent [%d] is about to exit |||\n", getpid(), getppid());
write(1, buf, strlen(buf));
}
else if (typeflag == FTW_DP || typeflag == FTW_D)
{
sprintf(buf, "%*s%s\n\n", ftwinfo->level * 4, "", filepath);
write(1, buf, strlen(buf));
}
}
return 0;
}
FTW_DP 和FTW_D 表示文件夹FTW_F 表示文件。基本上，我每次都尝试使用代码 fork()。如果它是父级，它等待其子级读取文件。因为该函数是递归的，所以它将分叉每个调用。但是，有一些关于它的东西，我不能让它分叉超过一个文件。例如，1a.txt 应该有一个孩子，但对于这个方案，它是 8。分叉主题真的很困难。我做日常练习并试图理解它。您的解释和帮助将提高我在该分支的技能。
@edit: mcve 代码
#define _POSIX_C_SOURCE 200809L
#define _XOPEN_SOURCE 700
#include <unistd.h>
#include <dirent.h>
#include <stdlib.h>
#include <locale.h>
#include <string.h>
#include <ftw.h>
#include <stdio.h>
#define TOTALNUMBEROFLINES 1000
#define BUFSIZE 1000
void err_sys(const char *const str)
{
perror(str);
fflush(stdout);
exit(1);
}
int storeLinesInArray(const char *file, char lines[][BUFSIZE])
{
return 0;
}
static int for_each_file(const char *filepath, int totalLines, const char *key, const char arr[][BUFSIZE])
{
fprintf(stdout, "File name is = %s\n", filepath);
fflush(stdout);
return 0;
}
static int soner_each_time(const char *filepath, const struct stat *info,
int typeflag, struct FTW *ftwinfo)
{
pid_t pid = 0;
char buf[BUFSIZE];
int status;
/* The variables are related to functions of reading file */
int totalLines;
char arr[TOTALNUMBEROFLINES][BUFSIZE];
int retval;
const char *const filename = filepath + ftwinfo->base;
if (( pid = fork()) < 0) {
perror("failed fork");
exit(-1);
}
else if( pid > 0 ) // parent
{
if (typeflag == FTW_DP || typeflag == FTW_D)
{
sprintf(buf, "%*s%s\n\n", ftwinfo->level * 4, "", filepath);
write(1, buf, strlen(buf));
pid = wait(&status);
if (pid == -1)
perror("Failed to wait for child");
else if (WIFEXITED(status) && !WEXITSTATUS(status))
printf("parent [%d] reaped child [%d]\n", getpid(), pid);
else if (WIFEXITED(status))
printf("Child %ld terminated with return status %d\n",
(long)pid, WEXITSTATUS(status));
else if (WIFSIGNALED(status))
printf("Child %ld terminated due to uncaught signal %d\n",
(long)pid, WTERMSIG(status));
else if (WIFSTOPPED(status))
printf("Child %ld stopped due to signal %d\n",
(long)pid, WSTOPSIG(status));
}
}
if (pid == 0) // child
{
if (typeflag == FTW_F)
{
sprintf(buf, "||| Child [%d] of parent [%d]: %s |||\n", getpid(), getppid(), filename);
write(1, buf, strlen(buf));
/* Both of them are about reading function */
totalLines = storeLinesInArray(filename, arr);
retval = for_each_file(filename, totalLines, "not needed now", arr);
sprintf(buf, "||| Child [%d] of parent [%d] is about to exit |||\n", getpid(), getppid());
write(1, buf, strlen(buf));
}
else if (typeflag == FTW_DP || typeflag == FTW_D)
{
sprintf(buf, "%*s%s\n\n", ftwinfo->level * 4, "", filepath);
write(1, buf, strlen(buf));
}
}
return 0;
}
int main(int argc, char *argv[])
{
if (nftw("here is directory path", soner_each_time, 15, FTW_CHDIR)) {
fprintf(stderr, "Failed directory.\n");
exit(-1);
}
return 0;
}
【问题讨论】：
-
“有一些关于它的东西，我不能让它分叉超过一个文件”。这到底是什么意思呢？也许会有助于给出预期行为和实际行为的具体示例。
-
我已经编辑了问题@kaylum
-
甚至不知道从哪里开始...您有一个
status变量，您可以对其进行测试但从未设置过；您似乎正在检查孩子状态而没有等待孩子完成。 -
你需要发布一个完整的、可编译的示例——MCVE。
-
@snr 因为这是 * 通常的工作方式（阅读 MVCE 链接）。如果我能运行你的代码，我可能会很快告诉你它有什么问题；如果我不能运行你的代码，我可能不会费心去想办法。 （请注意，您的示例也应该是minimal。正如链接所说，减少它通常会帮助您自己解决问题。