Reading contents from multiple pipes, C

I have a program where I need to read the contents of several pipes, compare the words, print smallest word, get a new word from that pipe (and that pipe only), compare again, until all pipes are empty. I have a couple issues: 1: For some reason I can only read from one pipe. When trying to read from the others, it keeps giving me nothing, even though if I set the pipe to be any of the others, it works with that pipe only. Basically, I can't get sortOutput to switch to the other pipes when I want it to. 2: For some reason I cannot seem to detect when an array element is empty so it compares "" to the word, and "" is always lower. As far as I can tell, what is happening is that sortOutput is set to the last pipe, and then it keeps reading from that pipe instead of the other pipes, or nothing if forced to read from the other pipes via the loop. I'm unsure why, but if I set sortOutput explicitly to a different pipe (without a loop, declared globally), it will read all words from any of the other pipes just fine. It's switching sortOutput to other pipes within the loop that is causing the problems, I think. Strangely enough, when setting up the initial word array, switching sortOutput to other pipes works just fine. As a note, I have to use fgets, I don't have a choice in that. Here's the code for the suppressor, I have commented where I believe the problem to be happening: //Suppressor - Reads one word from each pipe, compares, prints largest. Gets next word from that one pipe, compares, prints largest. //Suppressor deletes duplicate words //Reads from pipefds_two[count*2] position char* words[numChildren]; int index, cont=1; char* smallest; int smallestIndex; int checker; int duplicateCount = 0; int kindex; char* temptwo; int length; int nullCount = 0; int counter = 0; FILE* sortOutput; for(kindex = 0; kindex < numChildren; kindex++){ //Initializes array with beginning values sortOutput = fdopen(pipefds_two[kindex*2], "r"); fgets(buffer, PIPE_BUF, sortOutput); words[kindex] = strdup(buffer); //fflush(sortOutput); close(pipefds_two[(kindex*2)+1]); } while(counter < 13){ //This is where it prints out lowest values each "round", gets new words, and gets rid of duplicates printf("\nCurrent words in array (0, 1, 2): %s %s %s", words[0], words[1], words[2]); for(index = 0; index < numChildren; index++){ if(words[index] != NULL){ //Searches for first value in array that's not null to be "lowest" value smallest = words[index]; smallestIndex = index; printf("Found first non-null word: %s", smallest); break; } } printf("Suppressor WHILE \n"); nullCount = 0; printf("smallest word assigned: %s ", smallest); printf("smallest index %d\n", smallestIndex); for(index = 0; index < numChildren; index++){ //need to loop through each pipe and pull a word, THEN compare them all! printf("Suppressor FOR (index: %d word:%s)", index, words[index]); if(words[index] == NULL){ //Fills in a NULL gap in the array with a new word from the corresponding pipe bzero(buffer, PIPE_BUF); sortOutput = fdopen(pipefds_two[index*2], "r"); //THIS IS PROBLEM! Here, or around here! fgets(buffer, PIPE_BUF, sortOutput); words[index] = strdup(buffer); //fflush(sortOutput); printf("the word which replaces a NULL: %s", buffer); } } for(index = 0; index < numChildren; index++){ //COMPARE ALL VALUES NOW THAT IT IS POPULATED printf("compare FOR loop index: %d\n", index); if((index != numChildren) && (words[index] != NULL) && (index != smallestIndex)){ printf("IF statement, (current arrayWord: %s)(smallest: %s)", words[index], smallest); checker = strcmp(smallest, words[index]); //printf("checker\n"); if(checker > 0){ smallest = words[index]; smallestIndex = index; printf("New smallest assigned: %s New Smallest Index: %d\n", smallest, smallestIndex); }else if(checker == 0){ printf("Same word\n"); words[index] = NULL; duplicateCount++; }else{ printf("ArrayWord is larger, smallest staying the same\n"); } } if(index == numChildren-1){ //reached the end of the list printf("The smallest this round is: %s", smallest); words[smallestIndex] = NULL; } } for(index = 0; index

以上就是Reading contents from multiple pipes, C的详细内容,更多请关注web前端其它相关文章!

赞(0) 打赏
未经允许不得转载:web前端首页 » CSS3 答疑

评论 抢沙发

  • 昵称 (必填)
  • 邮箱 (必填)
  • 网址

前端开发相关广告投放 更专业 更精准

联系我们

觉得文章有用就打赏一下文章作者

支付宝扫一扫打赏

微信扫一扫打赏