在 C 中通过 argv 使用管道发送和接收字符数组
Sending and receiving character array using piping through argv in C
因此,我正在尝试创建一个管道,通过通过 argv[] 连接的管道来回发送 char 数组。现在,我一直在接收 interface.c 中的数组(从父级发送到 c_param 的参数到子级。)到在 db.c 中接收字符 3 和 5。我知道 3 和 5 是我的管道所在的 argv[] 的索引,但我不确定如何获取它并在 db.c 中打印出我的消息。
interface.c 创建管道,分叉为父进程和子进程。 char数组param传给子进程的char数组c_param。使用 snprintf,我将我的管道变成了一个 char,以便使用 execl 和我的 char 数组 c_param 发送。
interface.c:
int main (int argc, char *argv[])
{
int to_Child[2];
int to_Parent[2];
int id, toChildPipe, toParentPipe, err;
char param[100] = "This is the parameter!";
char sendPipe[100];
char recPipe[100];
/*CREATING PIPE*/
toChildPipe = pipe(to_Child);
toParentPipe = pipe(to_Parent);
if(toChildPipe == -1 || toParentPipe == -1)
{
printf ("Error on pipe creation: %d", errno);
exit (1);
}
/*Creating Child Process*/
id = fork();
if(id == 0)
{
/**
*
* IN THE CHILD Process
*
*/
close(to_Child[1]); //reading
close(to_Parent[0]); //writing
char c_param[100];
toChildPipe = read(to_Child[0], c_param, 100);
if (toChildPipe == -1)
{
//If failed
printf("Error on read from pipe from parent: %d\n",errno);
//exit with error
exit(2);
}//Error pipe from parent
snprintf(sendPipe,sizeof(sendPipe), "%d",to_Parent[0]);
snprintf(recPipe,sizeof(recPipe), "%d",to_Child[0]);
err = execl("./db","db",sendPipe,recPipe,(char *)0);
if(err == -1)
{
printf("Error on execl: %d\n", errno);
}//Error execl
toChildPipe = read(to_Child[0], c_param, 100);
if (toChildPipe == -1)
{
//If failed
printf("Error on read from pipe from parent: %d\n",errno);
//exit with error
exit(2);
}//Error pipe from parent
}//CHILD PROCESS
else if (id > 0)
{
/**
*
*IN THE PARENT PROCESS
*
*/
close(to_Child[0]); //writing
close(to_Parent[1]); //reading
toChildPipe = write(to_Child[1],param,100);
if(toChildPipe == -1)
{
printf("Error on write to pipe: %d", errno);
exit(3);
}
/*Piping was successful!*/
exit(0);
}//PARENT PROCESS
else
{
exit(4);
}
}
db.c 从 interface.c execl 启动,应该通过 argv[] 接收参数,然后将其打印出来。
db.c
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
FILE *finput;
int j = 0;
int fd;
int toChildPipe;
char c_param[100];
if(argc > 1)
{
for(j ; j < argc ; j++)
printf("argv = %s\n", argv[j]);
printf("argc = %d\n",argc);
}
fd = atoi(argv[1]);
printf("Statement: %s\n", argv[fd]);
strcpy(c_param, argv[3]);
printf("filename: %s\n", c_param);
}
这是我得到的当前输出,我知道 5 和 3 是我需要发送消息和接收消息的索引,我目前正在尝试在 db.c 中打印
输出(db.c):
argv = db
argv = 5
argv = 3
argc = 3
Statement: TERM=xterm
我希望我给了你足够的信息,我很感激你愿意给我的任何帮助。提前致谢!
有很多小问题。你最大的问题是你在 db.c
中的 assumptions/assertions 关于 interface.c
传递给它的参数——传递的和预期的完全不匹配。 interface.c
中还有大量无关代码。特别是,child 在执行 db
之前从管道读取,因此管道上没有任何内容可供 db
读取。
这是 'fixed' 代码,一些调试代码仍然存在。
interface.c
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
int main(void)
{
int to_Child[2];
int to_Parent[2];
int id;
char param[100] = "This is the parameter!";
char sendPipe[100];
char recPipe[100];
if (pipe(to_Child) == -1 || pipe(to_Parent) == -1)
{
printf("Error on pipe creation: %d", errno);
exit(1);
}
printf("Pipes: C(%d,%d), P(%d,%d)\n", to_Child[0], to_Child[1], to_Parent[0], to_Parent[1]);
id = fork();
if (id == 0)
{
close(to_Child[1]); // Child does not write to itself
close(to_Parent[0]); // Child does not read what it writes
snprintf(sendPipe, sizeof(sendPipe), "%d", to_Parent[1]);
snprintf(recPipe, sizeof(recPipe), "%d", to_Child[0]);
execl("./db", "db", sendPipe, recPipe, (char *)0);
fprintf(stderr, "Error on execl: %d\n", errno);
exit(2);
}
else if (id > 0)
{
close(to_Child[0]); // Parent does not read childs input
close(to_Parent[1]); // Parent does not
int nbytes = write(to_Child[1], param, 100);
if (nbytes == -1)
{
fprintf(stderr, "Error on write to pipe: %d\n", errno);
exit(3);
}
close(to_Child[1]);
if ((nbytes = read(to_Parent[0], param, 100)) <= 0)
{
fprintf(stderr, "Error on read from pipe: %d\n", errno);
exit(5);
}
printf("Data from pipe: [%.*s]\n", nbytes, param);
exit(0);
}
else
{
perror("fork failed");
exit(4);
}
}
### db.c
#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
printf("argc = %d\n", argc);
for (int j = 0; j < argc; j++)
printf("argv[%d] = %s\n", j, argv[j]);
if (argc != 3)
{
fprintf(stderr, "Usage: %s write-fd read-fd\n", argv[0]);
return 1;
}
int ofd = atoi(argv[1]);
int ifd = atoi(argv[2]);
printf("ifd = %d; ofd = %d\n", ifd, ofd);
char c_param[100];
int nbytes = read(ifd, c_param, sizeof(c_param));
if (nbytes <= 0)
{
fprintf(stderr, "Error: failed to read any data (%d)\n", errno);
return 1;
}
printf("Child: [%.*s]\n", nbytes, c_param);
assert(strlen(c_param) + sizeof(" - sent back to parent") <= sizeof(c_param));
strcat(c_param, " - sent back to parent");
if (write(ofd, c_param, nbytes) != nbytes)
{
fprintf(stderr, "Error: failed to write all the data (%d)\n", errno);
return 1;
}
return 0;
}
样本运行
Pipes: C(3,4), P(5,6)
argc = 3
argv[0] = db
argv[1] = 6
argv[2] = 3
ifd = 3; ofd = 6
Child: [This is the parameter!]
Data from pipe: [This is the parameter! - sent back to parent]
请注意,代码向标准错误报告错误(这就是它的用途)。它还对打印的数据进行了分隔,这样更容易识别
意想不到的问题。它不假设数据是空填充的;它将打印的长度限制为读取的长度,但实际上数据末尾有许多空值。
因此,我正在尝试创建一个管道,通过通过 argv[] 连接的管道来回发送 char 数组。现在,我一直在接收 interface.c 中的数组(从父级发送到 c_param 的参数到子级。)到在 db.c 中接收字符 3 和 5。我知道 3 和 5 是我的管道所在的 argv[] 的索引,但我不确定如何获取它并在 db.c 中打印出我的消息。
interface.c 创建管道,分叉为父进程和子进程。 char数组param传给子进程的char数组c_param。使用 snprintf,我将我的管道变成了一个 char,以便使用 execl 和我的 char 数组 c_param 发送。
interface.c:
int main (int argc, char *argv[])
{
int to_Child[2];
int to_Parent[2];
int id, toChildPipe, toParentPipe, err;
char param[100] = "This is the parameter!";
char sendPipe[100];
char recPipe[100];
/*CREATING PIPE*/
toChildPipe = pipe(to_Child);
toParentPipe = pipe(to_Parent);
if(toChildPipe == -1 || toParentPipe == -1)
{
printf ("Error on pipe creation: %d", errno);
exit (1);
}
/*Creating Child Process*/
id = fork();
if(id == 0)
{
/**
*
* IN THE CHILD Process
*
*/
close(to_Child[1]); //reading
close(to_Parent[0]); //writing
char c_param[100];
toChildPipe = read(to_Child[0], c_param, 100);
if (toChildPipe == -1)
{
//If failed
printf("Error on read from pipe from parent: %d\n",errno);
//exit with error
exit(2);
}//Error pipe from parent
snprintf(sendPipe,sizeof(sendPipe), "%d",to_Parent[0]);
snprintf(recPipe,sizeof(recPipe), "%d",to_Child[0]);
err = execl("./db","db",sendPipe,recPipe,(char *)0);
if(err == -1)
{
printf("Error on execl: %d\n", errno);
}//Error execl
toChildPipe = read(to_Child[0], c_param, 100);
if (toChildPipe == -1)
{
//If failed
printf("Error on read from pipe from parent: %d\n",errno);
//exit with error
exit(2);
}//Error pipe from parent
}//CHILD PROCESS
else if (id > 0)
{
/**
*
*IN THE PARENT PROCESS
*
*/
close(to_Child[0]); //writing
close(to_Parent[1]); //reading
toChildPipe = write(to_Child[1],param,100);
if(toChildPipe == -1)
{
printf("Error on write to pipe: %d", errno);
exit(3);
}
/*Piping was successful!*/
exit(0);
}//PARENT PROCESS
else
{
exit(4);
}
}
db.c 从 interface.c execl 启动,应该通过 argv[] 接收参数,然后将其打印出来。 db.c
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
FILE *finput;
int j = 0;
int fd;
int toChildPipe;
char c_param[100];
if(argc > 1)
{
for(j ; j < argc ; j++)
printf("argv = %s\n", argv[j]);
printf("argc = %d\n",argc);
}
fd = atoi(argv[1]);
printf("Statement: %s\n", argv[fd]);
strcpy(c_param, argv[3]);
printf("filename: %s\n", c_param);
}
这是我得到的当前输出,我知道 5 和 3 是我需要发送消息和接收消息的索引,我目前正在尝试在 db.c 中打印
输出(db.c):
argv = db
argv = 5
argv = 3
argc = 3
Statement: TERM=xterm
我希望我给了你足够的信息,我很感激你愿意给我的任何帮助。提前致谢!
有很多小问题。你最大的问题是你在 db.c
中的 assumptions/assertions 关于 interface.c
传递给它的参数——传递的和预期的完全不匹配。 interface.c
中还有大量无关代码。特别是,child 在执行 db
之前从管道读取,因此管道上没有任何内容可供 db
读取。
这是 'fixed' 代码,一些调试代码仍然存在。
interface.c
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
int main(void)
{
int to_Child[2];
int to_Parent[2];
int id;
char param[100] = "This is the parameter!";
char sendPipe[100];
char recPipe[100];
if (pipe(to_Child) == -1 || pipe(to_Parent) == -1)
{
printf("Error on pipe creation: %d", errno);
exit(1);
}
printf("Pipes: C(%d,%d), P(%d,%d)\n", to_Child[0], to_Child[1], to_Parent[0], to_Parent[1]);
id = fork();
if (id == 0)
{
close(to_Child[1]); // Child does not write to itself
close(to_Parent[0]); // Child does not read what it writes
snprintf(sendPipe, sizeof(sendPipe), "%d", to_Parent[1]);
snprintf(recPipe, sizeof(recPipe), "%d", to_Child[0]);
execl("./db", "db", sendPipe, recPipe, (char *)0);
fprintf(stderr, "Error on execl: %d\n", errno);
exit(2);
}
else if (id > 0)
{
close(to_Child[0]); // Parent does not read childs input
close(to_Parent[1]); // Parent does not
int nbytes = write(to_Child[1], param, 100);
if (nbytes == -1)
{
fprintf(stderr, "Error on write to pipe: %d\n", errno);
exit(3);
}
close(to_Child[1]);
if ((nbytes = read(to_Parent[0], param, 100)) <= 0)
{
fprintf(stderr, "Error on read from pipe: %d\n", errno);
exit(5);
}
printf("Data from pipe: [%.*s]\n", nbytes, param);
exit(0);
}
else
{
perror("fork failed");
exit(4);
}
}
### db.c
#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
printf("argc = %d\n", argc);
for (int j = 0; j < argc; j++)
printf("argv[%d] = %s\n", j, argv[j]);
if (argc != 3)
{
fprintf(stderr, "Usage: %s write-fd read-fd\n", argv[0]);
return 1;
}
int ofd = atoi(argv[1]);
int ifd = atoi(argv[2]);
printf("ifd = %d; ofd = %d\n", ifd, ofd);
char c_param[100];
int nbytes = read(ifd, c_param, sizeof(c_param));
if (nbytes <= 0)
{
fprintf(stderr, "Error: failed to read any data (%d)\n", errno);
return 1;
}
printf("Child: [%.*s]\n", nbytes, c_param);
assert(strlen(c_param) + sizeof(" - sent back to parent") <= sizeof(c_param));
strcat(c_param, " - sent back to parent");
if (write(ofd, c_param, nbytes) != nbytes)
{
fprintf(stderr, "Error: failed to write all the data (%d)\n", errno);
return 1;
}
return 0;
}
样本运行
Pipes: C(3,4), P(5,6)
argc = 3
argv[0] = db
argv[1] = 6
argv[2] = 3
ifd = 3; ofd = 6
Child: [This is the parameter!]
Data from pipe: [This is the parameter! - sent back to parent]
请注意,代码向标准错误报告错误(这就是它的用途)。它还对打印的数据进行了分隔,这样更容易识别 意想不到的问题。它不假设数据是空填充的;它将打印的长度限制为读取的长度,但实际上数据末尾有许多空值。