标签: pipe

鉴于此代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>

#define BUF_SIZE 256

int main()
{
    int fd1[2];
    int fd2[2];

    ssize_t numRead = -1;

    // remark : working under the assumption that the messages are of equal length

    const char* messageOne = "Hello world , I'm child number 1\n";
    const char* messageTwo = "Hello world , I'm child number 2\n";

    const unsigned int commLen = strlen(messageOne) + 1;

    char buf[BUF_SIZE];

    if (pipe(fd1) == -1)
    {
        printf("Error opening pipe 1!\n"); …

我正在尝试通过管道进行2个进程通信.我等待孩子在管道中写一个字符,然后父母将从管道中读取字符并将其显示在屏幕上.问题是我成功地在管道中写入了字符(我做了一个测试,立即从中读取,我看到它在管道中),但是当父管从管道中读取时,它内部没有任何内容.我真的不明白为什么; 一切似乎都很好.

int PID, canal[2];
if(-1 == (PID = fork()))
{
    perror("Error");
    return 0;
}
if(-1 == pipe(canal))
{
    perror("Error");
    return 0;
}
if(PID == 0)
{
    close(canal[0]);
    printf("Child\n");
    char buffer = 'C';
    if( 0 == write(canal[1], &buffer, sizeof(char)))
        printf("Didn't write anything\n");
    close(canal[1]);
}
else
{
    char readBuffer;
    wait(NULL);
    printf("Parent\n");
    close(canal[1]);
    if(read(canal[0], &readBuffer, sizeof(char)))
    {
        printf("I read: ");
        printf("%c\n", readBuffer);
    }
    close(canal[0]);
}

嗨,我想把我计算的数字四舍五入到千位.

例如,如果我得到545,000,我希望它是550,000

我创造了一个管道

import {Pipe, PipeTransform} from '@angular/core';

@Pipe({name: 'round'})
export class RoundPipe implements PipeTransform {

    transform(value: number): number {
        return Math.round(value);
    }
}

似乎没有用

任何的想法？

我有一个管道转换货币如下,

import { Pipe, PipeTransform } from '@angular/core';
import { LocalStorageService } from 'storage.service';
import { CurrencyUpdate } from 'update';
import { Observable } from 'rxjs/Observable';

@Pipe({name: 'currConvert'})
export class CurrConvertPipe implements PipeTransform {
    errorMessage: string;

    constructor(private currencyStorage: LocalStorageService, private currencyConversion: CurrencyUpdate) {
    }

    transform(value: number, toCurrency: string, baseCurrency: string): any {
        if (toCurrency && baseCurrency) {
            const outputRate = this.currencyStorage.getCurrencyRate(baseCurrency, toCurrency);
            if (!outputRate) {
                return this.currencyConversion.getExchangeRate(toCurrency, baseCurrency).map((rate: any) => {
                    const currency = {
                        fromCurrency: baseCurrency,
                        toCurrency,
                        exchangeRate: rate …

在角度2或4中我希望数字用逗号分隔,当它在输入和用户输入时以及它只是打印时.您有任何想法或解决方案可以分享吗？提前谢谢你们.

正如本回答中所解释的那样,在编写器进程关闭所有相关文件描述符EOF之后,我期待读者进程能够正确捕获.

但这并没有发生,这个程序最终陷入无休止的循环.父母等待孩子完成,孩子等待发出EOF封闭管道的信号.

为什么读者进程没有收到EOF？

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <wait.h>

#define STRING_TO_SEND "Hello, world!\n"

int main() {
    int fd[2], i = 0;
    __pid_t pid;
    char _char;
    ssize_t nbytes;

    pipe(fd);
    pid = fork();

    if (pid == -1) {
        // Error
        perror("Error forking!");
        return EXIT_FAILURE;

    } else if (pid == 0) {

        // Child
        close(fd[1]);
        while ((nbytes = read(fd[0], &_char, 1)) != EOF) {
            if (nbytes == 0) …

假设我有一个文件t.txt,其中包含许多包含'a'的行.我很疑惑为什么这不起作用:

cat <(tail -f t.txt | grep a)

上面的命令只是挂起而不打印任何内容,即使每行都有匹配.这是因为猫正在等待"尾巴"而不是"grep"的输出吗？我怎样才能解决这个问题？

顺便说一句,我尝试了另一种带有双重过程替换的变体:

cat <(grep a <(tail -f t.txt))

这也挂起而不打印任何东西.

有人有线索吗？

基本代码:

my $ContentDate = `date -d '1 hour ago' '+%Y-%m-%e %H:'`;
my $Fail2banNo = `grep Ban /var/log/fail2ban.log | grep $ContentDate | wc -l`;

if (($Fail2banNo > $fail2ban)) {

} else {

}

为什么Perl不会正确完成这些命令？$ fail2ban已经定义为0,所以这不是问题.

fail2ban.log确实包含一个应匹配的行(当从shell运行命令时它匹配):

2018-07-19 xx:11:50,200 fail2ban.actions[3725]: WARNING [iptables] Ban x.x.x.x

我一直得到的错误是:

grep: 10:: No such file or directory
sh: -c: line 1: syntax error near unexpected token `|'
sh: -c: line 1: ` | wc -l'
Argument "" isn't numeric in numeric gt (>) at /usr/local/bin/tmgSupervision.pl line 3431. …

在VB.Net中是否有相当于C#的管道运算符(|)？

我从这里有一些代码如何为我的应用程序为所有用户创建的文件授予完全权限？

它在C#中,我想将其转换为VB.Net.我到目前为止(VS说有一个错误:| InheritanceFlags.ContainerInherit):

Sub ZugriffsrechteEinstellen()

    Dim dInfo As New DirectoryInfo(strPfadSpracheINI)
    Dim dSecurity As New DirectorySecurity

    dSecurity = dInfo.GetAccessControl()
    dSecurity.AddAccessRule(New FileSystemAccessRule(New SecurityIdentifier(WellKnownSidType.WorldSid, Nothing), FileSystemRights.FullControl, InheritanceFlags.ObjectInherit | InheritanceFlags.ContainerInherit, PropagationFlags.NoPropagateInherit, AccessControlType.Allow))

    dInfo.SetAccessControl(dSecurity)

End Sub

我有以下程序：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <assert.h>
#include <errno.h>
#include <sys/wait.h>

int main()
{
    int p[2];
    char *argv[2];
    argv[0] = "wc";
    argv[1] = "-w";
    argv[2] = NULL;

    pipe(p);
    if (fork() == 0)
    {
        close(0);
        dup(p[0]);
        close(p[0]);
        close(p[1]);
        execvp(argv[0], argv);
    }
    else
    {
        close(p[0]);
        write(p[1], "hello world\n", 12);
    }

    fprintf(stdout, "hello world\n");
}

当我运行它时：

$ gcc a.c
$ ./a.out

我得到以下内容：

hello world
$ 2
_    // the cursor is flickering here

输入后Enter …