C初学者。我的C程序应该逐行读取文件input.txt，然后在mapper_pipes中写一行。有四行文本，每行都被发送到不同的映射管道。分叉4个进程，每个进程对应一个文本行。程序正在从文件中正确读取文本行，我知道因为我在send_line_to_mapper函数中控制它们。自printf("hello from mapper/n");打印以来，mapper forks内部的代码似乎正在工作，但它不会打印通过此处管道发送的消息printf("forked mapper read line: %s\n", ibuf);。感谢任何帮助。
*编辑：我在叉子后立即接近，现在正在工作。 在写入管道后以及从管道读取的分叉过程之后关闭写入管道末端，仍然没有读取EOF。
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <errno.h>
#define BUFFER_SIZE 1024
#define ALPHA_OFFSET 97
#define LETTERS 26
const int NUM_OF_MAPPERS = 4;
const int NUM_OF_REDUCERS = 26;
const int PIPE_READ_END = 0;
const int PIPE_WRITE_END = 1;
const int PIPE_BUFFER_SIZE = 1000;
int mapper_pipes[4][2];
int reducer_pipes[26][2];
void pipe_wrapper(int pipefd[]) {
int ret = pipe(pipefd);
if (ret == -1) {
perror("Error. Failed when trying to create pipes.");
exit(EXIT_FAILURE);
}
}
void create_mapper_pipes(void) {
int i;
for (i = 0; i < NUM_OF_MAPPERS; i++) {
pipe_wrapper(mapper_pipes[i]);
}
}
void create_reducer_pipes(void) {
int i;
for (i=0; i < NUM_OF_REDUCERS; i++) {
pipe_wrapper(reducer_pipes[i]);
}
}
// Prints an error msg and exits if one occurs. Else, returns the system call value.
int print_if_err(int syscall_val, const char* syscall_name) {
if (syscall_val < 0) {
perror(syscall_name);
exit(errno);
} else {
//No syscall error we can return
return syscall_val;
}
}
void fork_mappers(void) {
/* Constants useful to all children */
char ibuf[PIPE_BUFFER_SIZE]; // input pipe buffer
int rlen = 0;
int i;
for (i=0; i<NUM_OF_MAPPERS; i++) {
pid_t mapper_pid = print_if_err(fork(), "fork");
if (mapper_pid == 0) {
close(mapper_pipes[i][PIPE_WRITE_END]);
rlen = print_if_err(read(mapper_pipes[i][PIPE_READ_END], ibuf, 1000), "read");
while(rlen > 0) {
printf("read line from forked_mappers, p%d: %s\n", i, ibuf);
rlen = print_if_err(read(mapper_pipes[i][PIPE_READ_END], ibuf, 1000), "read");
}
_exit(0);
}
}
}
void fork_reducers(void) {
int i;
for (i = 0; i < NUM_OF_REDUCERS; i++) {
pid_t reducer_pid = print_if_err(fork(), "fork");
if (reducer_pid == 0) {
}
}
}
void send_lines_to_mappers(void) {
int wlen = 0;
char obuf[PIPE_BUFFER_SIZE];
int ob_size;
int count = 0;
char buff[BUFFER_SIZE]; // a buffer for each line of the file
FILE *input_file = fopen("input.txt", "r");
// read the input file line by line
while(fgets(buff, BUFFER_SIZE, input_file) > 0) {
printf("read line from send_lin_to_mappers: %s\n", buff);
ob_size = sizeof buff;
switch(count) {
case 0 :
write(mapper_pipes[0][PIPE_WRITE_END], buff, ob_size);
close(mapper_pipes[0][PIPE_WRITE_END]);
break;
case 1 :
write(mapper_pipes[1][PIPE_WRITE_END], buff, ob_size);
close(mapper_pipes[1][PIPE_WRITE_END]);
break;
case 2 :
write(mapper_pipes[2][PIPE_WRITE_END], buff, ob_size);
close(mapper_pipes[2][PIPE_WRITE_END]);
break;
case 3 :
write(mapper_pipes[3][PIPE_WRITE_END], buff, ob_size);
close(mapper_pipes[3][PIPE_WRITE_END]);
break;
default :
printf("you did something wrong in send_lines_to_mappers loop");
}
count++;
}
fclose(input_file);
}
int main(void) {
// Setup the mapper pipes
create_mapper_pipes();
create_reducer_pipes();
fork_mappers();
//fork_reducers();
send_lines_to_mappers();
return 0;
}
现在一切似乎都在运作，但fork_mappers中的分叉流程从不会在循环和退出时离开。
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <errno.h>
#define BUFFER_SIZE 1024
#define ALPHA_OFFSET 97
#define LETTERS 26
const int NUM_OF_MAPPERS = 4;
const int NUM_OF_REDUCERS = 26;
const int PIPE_READ_END = 0;
const int PIPE_WRITE_END = 1;
const int PIPE_BUFFER_SIZE = 1000;
int mapper_pipes[4][2];
int reducer_pipes[26][2];
void pipe_wrapper(int pipefd[]) {
int ret = pipe(pipefd);
if (ret == -1) {
perror("Error. Failed when trying to create pipes.");
exit(EXIT_FAILURE);
}
}
void create_mapper_pipes(void) {
int i;
for (i = 0; i < NUM_OF_MAPPERS; i++) {
pipe_wrapper(mapper_pipes[i]);
}
}
void create_reducer_pipes(void) {
int i;
for (i=0; i < NUM_OF_REDUCERS; i++) {
pipe_wrapper(reducer_pipes[i]);
}
}
// Prints an error msg and exits if one occurs. Else, returns the system call value.
int print_if_err(int syscall_val, const char* syscall_name) {
if (syscall_val < 0) {
perror(syscall_name);
exit(errno);
} else {
//No syscall error we can return
return syscall_val;
}
}
void fork_mappers(void) {
/* Constants useful to all children */
char ibuf[PIPE_BUFFER_SIZE]; // input pipe buffer
int rlen = 0;
int i;
for (i=0; i<NUM_OF_MAPPERS; i++) {
pid_t mapper_pid = print_if_err(fork(), "fork");
if (mapper_pid == 0) {
rlen = print_if_err(read(mapper_pipes[i][PIPE_READ_END], ibuf, 1000), "read");
while(rlen > 0) {
printf("read line from forked_mappers, p%d: %s\n", i, ibuf);
rlen = print_if_err(read(mapper_pipes[i][PIPE_READ_END], ibuf, 1000), "read");
}
_exit(0);
}
}
}
void fork_reducers(void) {
int i;
for (i = 0; i < NUM_OF_REDUCERS; i++) {
pid_t reducer_pid = print_if_err(fork(), "fork");
if (reducer_pid == 0) {
}
}
}
void send_lines_to_mappers(void) {
int wlen = 0;
char obuf[PIPE_BUFFER_SIZE];
int ob_size;
int count = 0;
char buff[BUFFER_SIZE]; // a buffer for each line of the file
FILE *input_file = fopen("input.txt", "r");
// read the input file line by line
while(fgets(buff, BUFFER_SIZE, input_file) > 0) {
printf("read line from send_lin_to_mappers: %s\n", buff);
ob_size = sizeof buff;
switch(count) {
case 0 :
write(mapper_pipes[0][PIPE_WRITE_END], buff, ob_size);
break;
case 1 :
write(mapper_pipes[1][PIPE_WRITE_END], buff, ob_size);
break;
case 2 :
write(mapper_pipes[2][PIPE_WRITE_END], buff, ob_size);
break;
case 3 :
write(mapper_pipes[3][PIPE_WRITE_END], buff, ob_size);
break;
default :
printf("you did something wrong in send_lines_to_mappers loop");
}
count++;
}
fclose(input_file);
}
int main(void) {
// Setup the mapper pipes
create_mapper_pipes();
create_reducer_pipes();
fork_mappers();
//fork_reducers();
send_lines_to_mappers();
return 0;
}
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <errno.h>
#define BUFFER_SIZE 1024
#define ALPHA_OFFSET 97
#define LETTERS 26
const int NUM_OF_MAPPERS = 4;
const int NUM_OF_REDUCERS = 26;
const int PIPE_READ_END = 0;
const int PIPE_WRITE_END = 1;
const int PIPE_BUFFER_SIZE = 32;
int mapper_pipes[4][2];
int reducer_pipes[26][2];
void pipe_wrapper(int pipefd[]) {
int ret = pipe(pipefd);
if (ret == -1) {
perror("Error. Failed when trying to create pipes.");
exit(EXIT_FAILURE);
}
}
void create_mapper_pipes(void) {
int i;
for (i = 0; i < NUM_OF_MAPPERS; i++) {
pipe_wrapper(mapper_pipes[i]);
}
}
void create_reducer_pipes(void) {
int i;
for (i=0; i < NUM_OF_REDUCERS; i++) {
pipe_wrapper(reducer_pipes[i]);
}
}
// Prints an error msg and exits if one occurs. Else, returns the system call value.
int print_if_err(int syscall_val, const char* syscall_name) {
if (syscall_val < 0) {
perror(syscall_name);
exit(errno);
} else {
//No syscall error we can return
return syscall_val;
}
}
void fork_mappers(void) {
/* Constants useful to all children */
char ibuf[PIPE_BUFFER_SIZE]; // input pipe buffer
int rlen = 0;
int i;
for (i=0; i<NUM_OF_MAPPERS; i++) {
pid_t mapper_pid = print_if_err(fork(), "fork");
printf("%d\n", mapper_pid);
if (mapper_pid == 0) {
printf("hello from mapper/n");
rlen = print_if_err(read(mapper_pipes[i][PIPE_READ_END], ibuf, 1000), "read");
while(rlen > 0) {
printf("forked mapper read line: %s\n", ibuf);
rlen = print_if_err(read(mapper_pipes[i][PIPE_READ_END], ibuf, 1000), "read");
}
_exit(0);
}
}
}
void fork_reducers(void) {
int i;
for (i = 0; i < NUM_OF_REDUCERS; i++) {
pid_t reducer_pid = print_if_err(fork(), "fork");
if (reducer_pid == 0) {
}
}
}
void send_lines_to_mappers(void) {
int wlen = 0;
char obuf[PIPE_BUFFER_SIZE];
int obptr = 0;
int count = 0;
char buff[BUFFER_SIZE]; // a buffer for each line of the file
FILE *input_file = fopen("input.txt", "r");
// read the input file line by line
while(fgets(buff, BUFFER_SIZE, input_file) > 0) {
printf("read line: %s\n", buff);
switch(count) {
case 0 :
write(mapper_pipes[0][PIPE_WRITE_END], obuf, obptr);
break;
case 1 :
write(mapper_pipes[1][PIPE_WRITE_END], obuf, obptr);
break;
case 2 :
write(mapper_pipes[2][PIPE_WRITE_END], obuf, obptr);
break;
case 3 :
write(mapper_pipes[3][PIPE_WRITE_END], obuf, obptr);
break;
default :
printf("you did something wrong in send_lines_to_mappers loop");
}
count++;
}
fclose(input_file);
}
int main(void) {
// Setup the mapper pipes
create_mapper_pipes();
create_reducer_pipes();
fork_mappers();
//fork_reducers();
send_lines_to_mappers();
return 0;
}
9592
9593
9594
9595
read line: I like coding in C.
read line: I like manually allocating memory, and opening the registers window in Visual Studio to see the values of the eax register and blitting graphics to the screen and all the stuff that Dr. Dobbs wrote about in the 90s.
read line: My programming friends seem to believe that understanding this level of programming is good in a hand-wavy, theoretical sense, but when you consider all the web development, Java frameworks, and existing libraries most programmers today rely on, it's hard to really pin down a solid answer to the question "Why learn C?"
read line: This is my attempt to answer that question, and I believe it comes down to the basic programming concept of abstraction.
0
0
0
0