Хотя моя программа работает корректно во всех случаях, она не использует канал для соединения вывода первой из двух команд со второй, когда они разделены символом канала.Я записал вывод первой команды в файл, а затем перенаправил стандартный ввод второй команды в файл при запуске процесса для запуска этой команды.Мне нужно использовать системный вызов канала для создания канала и получения файловых дескрипторов для канала, а затем запустить два процесса одновременно.Это домашний вопрос, и я выполнил 99% работы, но каким-то образом не смог заставить работать системный вызов pipe ... я пытался сделать так, чтобы входные данные были такими: Command 1 |Команда 2 внутри дочернего процесса для команды 2: я закрываю FD [0], затем дублирую FD [1], а для команды 1 закрываю FD [1], затем дублирую FD [1] и закрываю FD [0].
Iя, черт возьми, путаюсь с файловыми дескрипторами при использовании канала .... Я должен использовать канал
Любая помощь приветствуется.Функция выполнения - это то место, где я разветвляю процессы.
Вот мой код ...
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <regex.h>
/* Global Variables */
extern char **environ; /* Environmental Variables */
char *pathList[10]; /* List of paths from the $PATH */
int pathCount; /* Count of the # of paths in $PATH */
char *pathSet; /* Variable through which $PATH is retrieved */
int hasPipe = 0;
int cmdNo = 0;
/* This function takes the 'finalPath', the full path to executable,argList[],the
full command-line input arguments and argCount, the number of arguments from
command-line as input. It the creates a child process, in turn invokes the
execve() that finally executes the executable in 'finalPath' with the arguments
in 'argText' all stored into the args[] appropriately. Child process also handles
input and output file re-direction.
*/
void execute(char *finalPath, char *argList[], int argCount)
{
int k,fd,ofound,pos,i; /* flags and temporary variables */
pid_t pid; /* process ID */
int status, which;
char msg[100];
char *args[4]; /* argument list for execve() */
int spCase = 0;
ofound = 0;
pos=0;
pid = fork(); /* Creating a new process using fork() */
if (pid == -1) /* Checking for errors in process creation */
{
write(1,"Fork failed.\n",12);
exit(1);
}
/**************************
Checking for parent process
***************************/
if (pid != 0)
{
which = wait(&status);
if (which == -1)
{
write(1,"Wait failed.\n",12);
exit(1);
}
if (status & 0xff)
{ /* Case of abnormal termination */
sprintf(msg,"ERROR: <dShell> # process %d terminated abnormally for reason %d\n",which, status & 0xff);
write(1,msg,strlen(msg));
}
else
{ /* Case of normal termination */
sprintf(msg,"process %d terminated normally with status %d\n",which, (status >> 8) & 0xff);
write(1,msg,strlen(msg));
}
}
/*************************
Checking for child process
**************************/
if (pid == 0)
{
char argText[50];
argText[0] = '\0';
int std_fd;
if(cmdNo==0 && hasPipe)
{
close(1);
std_fd = open("temp.out", O_WRONLY | O_CREAT | O_TRUNC, S_IRWXU);
dup(std_fd);
}
else if(cmdNo==1 && hasPipe)
{
close(0);
std_fd = open("temp.out", O_RDONLY);
dup(std_fd);
}
/* Finding the first re-direction operator */
for( i = 0; i < argCount ; ++i)
{
if( ofound != 1 && ofound != 2)
{
if( strcmp(argList[i],"<") == 0 )
{
fd = open(argList[i+1],O_RDONLY);
if (fd < 0)
{
sprintf(msg,"ERROR: %s could not be opened\n", argList[i+1]);
write(1, msg, strlen(msg));
exit(5);
}
ofound = 1;
strcpy(argText,"\0");
close(0);
dup(fd);
close(fd);
}
else if(strcmp(argList[i],">") == 0)
{
fd = open(argList[i+1],O_CREAT | O_WRONLY, 0777);
pos = i;
ofound = 2;
strcpy(argText,"\0");
if (fd < 0)
{
sprintf(msg,"ERROR: %s could not be opened\n", argList[i+1]);
write(1, msg, strlen(msg));
exit(5);
}
close(1);
dup(fd);
close(fd);
}
}
}
/* If input re-direction operator is found check for an output re-direction along with it */
if(ofound == 1)
{
for( k = 0; k < argCount && ofound != 2; ++k)
{
if( strcmp(argList[k],">") == 0 )
{
fd = open(argList[k+1],O_CREAT | O_WRONLY , 0777);
spCase = 1;
ofound = 2;
strcpy(argText,"\0");
if (fd < 0)
{
sprintf(msg,"ERROR: %s could not be opened\n", argList[k+1]);
write(1, msg, strlen(msg));
exit(5);
}
close(1);
dup(fd);
close(fd);
}
}
}
/* If the re-direction operators are not found */
if( ofound == 0 )
{
for(i = 1; i < argCount; ++i)
{
strcat(argText, argList[i]);
strcat(argText, " ");
}
spCase = 2;
}
/* Case when both arguments and output re-direction operators are found */
if (spCase == 0)
{
if(pos == 0)
{
for( i = 3; i<argCount; ++i)
{
strcat(argText, argList[i]);
strcat(argText," ");
}
}
if(pos == argCount - 2)
{
for( i = 1; i<argCount - 2; ++i)
{
strcat(argText, argList[i]);
strcat(argText," ");
}
}
}
argText[strlen(argText)-1] = '\0'; /*because I added an extra space so trimming that*/
/* Running the execve */
args[0] = finalPath;
if(strlen(argText) == 0) /* checking if argText is populated */
{
args[1] = NULL;
}
else
{
args[1] = argText;
args[2] = NULL;
}
/* Execute command,if it returns that means it failed and need to display error and exit */
execve(args[0], args, environ);
sprintf(msg, "ERROR! execve() failed");
write(1, msg, strlen(msg));
}
}
/*******************************************************************************
This function checks if the path is accessible and continues to execute the
command. If the path does not exist of is not accessible, variable 'retFlag'
is used to return 0 to the calling function.
********************************************************************************/
int checkPath(char *exepath, char *argList[], int argCount, int flag)
{
char *finalPath;
int retFlag = flag;
if(access(exepath,X_OK) == 0)
{
finalPath = exepath;
retFlag = 1;
execute(finalPath,argList,argCount);
return retFlag;
}
else
return retFlag;
}
/**********************************************************************************
This function checks if the first argument is a path and if so calls checkPath().
Else it gets the paths set to the $PATH variable, tokenizes it, pads it with the
first token of input command and calls checkPath(). If the correct path is established,
the variable 'found' is used to kick out of the for loop.
************************************************************************************/
void setPath(char *argList[], int argCount)
{
char *exepath;
char com[50];
char emsg[80];
char *command;
int i,found = 0;
/* Seperating the command if redirection is used */
if( strcmp(argList[0],"<") == 0 || strcmp(argList[0],">") == 0 )
{
command = argList[2];
}
else
command = argList[0];
/* In case of no redirection, storing the commands and arguments into a array */
if(strcmp(command,"#") == 0) /* Checking for comment statements */
{
write(1,"ERROR: No command(s) found. Only comment present/n",48);
}
else
{
if(strstr(command,"/")) /* Checking if the entire path is given as a part of the command */
{
exepath = command;
found = checkPath(exepath,argList,argCount,0);
}
else /* building the path and storing it in 'com' */
{
for(i = 0; i< pathCount && found != 1; i++)
{
sprintf(com,"%s%s%s",pathList[i],"/",command);
exepath = com;
found = checkPath(exepath,argList,argCount,0);
}
}
if(found == 0)
{
sprintf(emsg,"%s%s",command,":COMMAND DOES NOT EXIST");
write(1,emsg,sizeof(emsg));
write(1,"\n",1);
}
}
}
/* Tokenizes commands into words */
void tokens(char *cmdStr)
{
char cmd[100];
strcpy(cmd,cmdStr);
char *result;
char delims[] = " , ";
char *argList[20];
int argCount = 0;
/*Tokenize the individual command into strings */
result = strtok(cmd,delims);
while( result != NULL )
{
argList[argCount] = result;
result = strtok( NULL, delims );
++argCount;
}
setPath(argList,argCount);
}
/* Tokenizes multiple commands into single commands */
void tokenize(char *inputStr)
{
int i,cmdCount = 0;
char *cmdResult;
char *cmdStr[100];
char delimiters[] = "|";
cmdResult = strtok(inputStr, delimiters);
while(cmdResult != NULL)
{
cmdStr[cmdCount]=cmdResult;
cmdResult = strtok(NULL, delimiters);
cmdCount++;
}
if( cmdCount > 1 )
hasPipe = 1;
else
hasPipe = 0;
for( i=0; i<cmdCount ; i++)
{
cmdNo = i%cmdCount;
tokens(cmdStr[i]);
}
}
int main(int argc, char *argv[])
{
char prompt[8]; /* String that stores the personalized prompt */
char *path; /* Temporary variable used for tokenization*/
char ch; /* Temporary variable used in read() */
int chCount; /* # of characters read from the prompt */
int entry; /* return variable of read() */
int flag; /* Flag to go read the next command when newline is found */
regex_t reIgnore;
char pattern[20]="^\\s*$|^#.*";
/* Tokenizing the paths asociated with the $PATH and storing them in a array declared globally */
pathCount = 0;
pathSet = getenv("PATH");
if ( !pathSet)
{
write(1, "ERROR: PATH environment does not exist.\n", 40);
exit(1);
}
path = strtok(pathSet,":");
while(path != NULL)
{
pathList[pathCount] = path;
path = strtok(NULL,":");
++pathCount;
}
/* Checks for blanks and tabs in Step 2 */
if ( regcomp(&reIgnore, pattern, REG_EXTENDED) )
{
write(1, "Error. \n",9);
exit(2);
}
sprintf(prompt,"<dShell> # "); /* Storing the personalized shell prompt into 'prompt' */
/* Reading the input from command line and passing it to tokenize() */
while(1)
{
char inputStr[100]; /* String into which inputs are read into */
chCount = 0;
flag = 0;
hasPipe = 1;
write(1,prompt,strlen(prompt)); /* Printing out the personalized shell prompt */
/* This will read a character 1 by 1 until it reaches the end of file */
entry = read(0,&ch,1);
if(!entry)
exit(0);
/* Reading the input and storing it in inputStr as long as newline is not encountered */
while( entry != 0 && flag == 0 )
{
/* A newline has been found so a new command will need to be executed */
/* The inputStr till this point is sent to tokenize() */
if( ch == '\n' )
{
inputStr[chCount] = '\0';
flag = 1;
if(chCount > 0) {
if(strcmp(inputStr,"exit") == 0)
exit(3);
else
tokenize(inputStr);
}
}
inputStr[chCount] = ch;
chCount++;
if(flag == 0)
entry = read( 0, &ch, 1 );
}
}
}