我喜欢按需“记录”节目输出。例如。输出记录到终端，但另一个进程可以随时挂接当前输出。
经典的方式是：
myprogram 2>&1 | tee /tmp/mylog
并按需
tail /tmp/mylog
但是，即使在驱动器空间不足之前未使用，也会创建一个不断增长的日志文件。所以我的尝试是：
mkfifo /tmp/mylog
myprogram 2>&1 | tee /tmp/mylog
并按需
cat /tmp/mylog
现在我可以随时阅读/ tmp / mylog。但是，任何输出都会阻塞程序，直到读取/ tmp / mylog。我喜欢fifo来刷新任何未读回的数据。怎么做？
答案 0 :(得分：46)
受你的问题的启发，我写了一个简单的程序，可以让你这样做：
$ myprogram 2>&1 | ftee /tmp/mylog
它的行为类似于tee，但是将stdin克隆到stdout和命名管道（现在的要求）而没有阻塞。这意味着如果你想以这种方式记录，你可能会丢失你的日志数据，但我想这在你的场景中是可以接受的。
诀窍是阻止SIGPIPE信号并忽略写入损坏的fifo时的错误。当然，这个样本可以通过各种方式进行优化，但到目前为止，它的确可以完成这项工作。
/* ftee - clone stdin to stdout and to a named pipe
(c) racic@stackoverflow
WTFPL Licence */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <signal.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
int readfd, writefd;
struct stat status;
char *fifonam;
char buffer[BUFSIZ];
ssize_t bytes;
signal(SIGPIPE, SIG_IGN);
if(2!=argc)
{
printf("Usage:\n someprog 2>&1 | %s FIFO\n FIFO - path to a"
" named pipe, required argument\n", argv[0]);
exit(EXIT_FAILURE);
}
fifonam = argv[1];
readfd = open(fifonam, O_RDONLY | O_NONBLOCK);
if(-1==readfd)
{
perror("ftee: readfd: open()");
exit(EXIT_FAILURE);
}
if(-1==fstat(readfd, &status))
{
perror("ftee: fstat");
close(readfd);
exit(EXIT_FAILURE);
}
if(!S_ISFIFO(status.st_mode))
{
printf("ftee: %s in not a fifo!\n", fifonam);
close(readfd);
exit(EXIT_FAILURE);
}
writefd = open(fifonam, O_WRONLY | O_NONBLOCK);
if(-1==writefd)
{
perror("ftee: writefd: open()");
close(readfd);
exit(EXIT_FAILURE);
}
close(readfd);
while(1)
{
bytes = read(STDIN_FILENO, buffer, sizeof(buffer));
if (bytes < 0 && errno == EINTR)
continue;
if (bytes <= 0)
break;
bytes = write(STDOUT_FILENO, buffer, bytes);
if(-1==bytes)
perror("ftee: writing to stdout");
bytes = write(writefd, buffer, bytes);
if(-1==bytes);//Ignoring the errors
}
close(writefd);
return(0);
}
您可以使用以下标准命令进行编译：
$ gcc ftee.c -o ftee
您可以通过运行例如：
快速验证它 $ ping www.google.com | ftee /tmp/mylog
$ cat /tmp/mylog
另请注意 - 这不是多路复用器。您一次只能有一个进程$ cat /tmp/mylog。
答案 1 :(得分：11)
这是一个（非常）旧的主题，但我最近遇到了类似的问题。事实上，我需要的是将stdin克隆到stdout，并将副本复制到非阻塞的管道。第一个答案中提议的ftee真的有帮助，但是（对于我的用例）太不稳定了。意思是我丢失了数据，如果我及时完成的话我可以处理。
我遇到的情况是我有一个进程（some_process）聚合一些数据并每隔三秒将其结果写入stdout。 （简化）设置看起来像这样（在我使用命名管道的真实设置中）：
some_process | ftee >(onlineAnalysis.pl > results) | gzip > raw_data.gz
现在，raw_data.gz必须被压缩并且必须完整。 ftee做得很好。但是我在中间使用的管道太慢而无法抓取冲出的数据 - 但它足够快，可以处理所有内容，如果它可以到达它，这是用普通的T恤测试的。然而，如果未命名的管道发生任何事情，普通的T恤会阻塞，并且因为我希望能够按需挂钩，所以不能选择T恤。回到主题：当我在其间放置一个缓冲区时，它会变得更好，结果是：
some_process | ftee >(mbuffer -m 32M| onlineAnalysis.pl > results) | gzip > raw_data.gz
但那仍然在丢失我可以处理的数据。所以我继续将之前建议的ftee扩展到缓冲版本（bftee）。它仍具有所有相同的属性，但在写入失败时使用（低效？）内部缓冲区。如果缓冲区已满，它仍然会丢失数据，但它对我的情况很有效。一如往常有很大的改进空间，但是当我复制代码时，我想将它分享给可能有用的人。
/* bftee - clone stdin to stdout and to a buffered, non-blocking pipe
(c) racic@stackoverflow
(c) fabraxias@stackoverflow
WTFPL Licence */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <signal.h>
#include <unistd.h>
// the number of sBuffers that are being held at a maximum
#define BUFFER_SIZE 4096
#define BLOCK_SIZE 2048
typedef struct {
char data[BLOCK_SIZE];
int bytes;
} sBuffer;
typedef struct {
sBuffer *data; //array of buffers
int bufferSize; // number of buffer in data
int start; // index of the current start buffer
int end; // index of the current end buffer
int active; // number of active buffer (currently in use)
int maxUse; // maximum number of buffers ever used
int drops; // number of discarded buffer due to overflow
int sWrites; // number of buffer written to stdout
int pWrites; // number of buffers written to pipe
} sQueue;
void InitQueue(sQueue*, int); // initialized the Queue
void PushToQueue(sQueue*, sBuffer*, int); // pushes a buffer into Queue at the end
sBuffer *RetrieveFromQueue(sQueue*); // returns the first entry of the buffer and removes it or NULL is buffer is empty
sBuffer *PeakAtQueue(sQueue*); // returns the first entry of the buffer but does not remove it. Returns NULL on an empty buffer
void ShrinkInQueue(sQueue *queue, int); // shrinks the first entry of the buffer by n-bytes. Buffer is removed if it is empty
void DelFromQueue(sQueue *queue); // removes the first entry of the queue
static void sigUSR1(int); // signal handled for SUGUSR1 - used for stats output to stderr
static void sigINT(int); // signla handler for SIGKILL/SIGTERM - allows for a graceful stop ?
sQueue queue; // Buffer storing the overflow
volatile int quit; // for quiting the main loop
int main(int argc, char *argv[])
{
int readfd, writefd;
struct stat status;
char *fifonam;
sBuffer buffer;
ssize_t bytes;
int bufferSize = BUFFER_SIZE;
signal(SIGPIPE, SIG_IGN);
signal(SIGUSR1, sigUSR1);
signal(SIGTERM, sigINT);
signal(SIGINT, sigINT);
/** Handle commandline args and open the pipe for non blocking writing **/
if(argc < 2 || argc > 3)
{
printf("Usage:\n someprog 2>&1 | %s FIFO [BufferSize]\n"
"FIFO - path to a named pipe, required argument\n"
"BufferSize - temporary Internal buffer size in case write to FIFO fails\n", argv[0]);
exit(EXIT_FAILURE);
}
fifonam = argv[1];
if (argc == 3) {
bufferSize = atoi(argv[2]);
if (bufferSize == 0) bufferSize = BUFFER_SIZE;
}
readfd = open(fifonam, O_RDONLY | O_NONBLOCK);
if(-1==readfd)
{
perror("bftee: readfd: open()");
exit(EXIT_FAILURE);
}
if(-1==fstat(readfd, &status))
{
perror("bftee: fstat");
close(readfd);
exit(EXIT_FAILURE);
}
if(!S_ISFIFO(status.st_mode))
{
printf("bftee: %s in not a fifo!\n", fifonam);
close(readfd);
exit(EXIT_FAILURE);
}
writefd = open(fifonam, O_WRONLY | O_NONBLOCK);
if(-1==writefd)
{
perror("bftee: writefd: open()");
close(readfd);
exit(EXIT_FAILURE);
}
close(readfd);
InitQueue(&queue, bufferSize);
quit = 0;
while(!quit)
{
// read from STDIN
bytes = read(STDIN_FILENO, buffer.data, sizeof(buffer.data));
// if read failed due to interrupt, then retry, otherwise STDIN has closed and we should stop reading
if (bytes < 0 && errno == EINTR) continue;
if (bytes <= 0) break;
// save the number if read bytes in the current buffer to be processed
buffer.bytes = bytes;
// this is a blocking write. As long as buffer is smaller than 4096 Bytes, the write is atomic to a pipe in Linux
// thus, this cannot be interrupted. however, to be save this should handle the error cases of partial or interrupted write none the less.
bytes = write(STDOUT_FILENO, buffer.data, buffer.bytes);
queue.sWrites++;
if(-1==bytes) {
perror("ftee: writing to stdout");
break;
}
sBuffer *tmpBuffer = NULL;
// if the queue is empty (tmpBuffer gets set to NULL) the this does nothing - otherwise it tries to write
// the buffered data to the pipe. This continues until the Buffer is empty or the write fails.
// NOTE: bytes cannot be -1 (that would have failed just before) when the loop is entered.
while ((bytes != -1) && (tmpBuffer = PeakAtQueue(&queue)) != NULL) {
// write the oldest buffer to the pipe
bytes = write(writefd, tmpBuffer->data, tmpBuffer->bytes);
// the written bytes are equal to the buffer size, the write is successful - remove the buffer and continue
if (bytes == tmpBuffer->bytes) {
DelFromQueue(&queue);
queue.pWrites++;
} else if (bytes > 0) {
// on a positive bytes value there was a partial write. we shrink the current buffer
// and handle this as a write failure
ShrinkInQueue(&queue, bytes);
bytes = -1;
}
}
// There are several cases here:
// 1.) The Queue is empty -> bytes is still set from the write to STDOUT. in this case, we try to write the read data directly to the pipe
// 2.) The Queue was not empty but is now -> bytes is set from the last write (which was successful) and is bigger 0. also try to write the data
// 3.) The Queue was not empty and still is not -> there was a write error before (even partial), and bytes is -1. Thus this line is skipped.
if (bytes != -1) bytes = write(writefd, buffer.data, buffer.bytes);
// again, there are several cases what can happen here
// 1.) the write before was successful -> in this case bytes is equal to buffer.bytes and nothing happens
// 2.) the write just before is partial or failed all together - bytes is either -1 or smaller than buffer.bytes -> add the remaining data to the queue
// 3.) the write before did not happen as the buffer flush already had an error. In this case bytes is -1 -> add the remaining data to the queue
if (bytes != buffer.bytes)
PushToQueue(&queue, &buffer, bytes);
else
queue.pWrites++;
}
// once we are done with STDIN, try to flush the buffer to the named pipe
if (queue.active > 0) {
//set output buffer to block - here we wait until we can write everything to the named pipe
// --> this does not seem to work - just in case there is a busy loop that waits for buffer flush aswell.
int saved_flags = fcntl(writefd, F_GETFL);
int new_flags = saved_flags & ~O_NONBLOCK;
int res = fcntl(writefd, F_SETFL, new_flags);
sBuffer *tmpBuffer = NULL;
//TODO: this does not handle partial writes yet
while ((tmpBuffer = PeakAtQueue(&queue)) != NULL) {
int bytes = write(writefd, tmpBuffer->data, tmpBuffer->bytes);
if (bytes != -1) DelFromQueue(&queue);
}
}
close(writefd);
}
/** init a given Queue **/
void InitQueue (sQueue *queue, int bufferSize) {
queue->data = calloc(bufferSize, sizeof(sBuffer));
queue->bufferSize = bufferSize;
queue->start = 0;
queue->end = 0;
queue->active = 0;
queue->maxUse = 0;
queue->drops = 0;
queue->sWrites = 0;
queue->pWrites = 0;
}
/** push a buffer into the Queue**/
void PushToQueue(sQueue *queue, sBuffer *p, int offset)
{
if (offset < 0) offset = 0; // offset cannot be smaller than 0 - if that is the case, we were given an error code. Set it to 0 instead
if (offset == p->bytes) return; // in this case there are 0 bytes to add to the queue. Nothing to write
// this should never happen - offset cannot be bigger than the buffer itself. Panic action
if (offset > p->bytes) {perror("got more bytes to buffer than we read\n"); exit(EXIT_FAILURE);}
// debug output on a partial write. TODO: remove this line
// if (offset > 0 ) fprintf(stderr, "partial write to buffer\n");
// copy the data from the buffer into the queue and remember its size
memcpy(queue->data[queue->end].data, p->data + offset , p->bytes-offset);
queue->data[queue->end].bytes = p->bytes - offset;
// move the buffer forward
queue->end = (queue->end + 1) % queue->bufferSize;
// there is still space in the buffer
if (queue->active < queue->bufferSize)
{
queue->active++;
if (queue->active > queue->maxUse) queue->maxUse = queue->active;
} else {
// Overwriting the oldest. Move start to next-oldest
queue->start = (queue->start + 1) % queue->bufferSize;
queue->drops++;
}
}
/** return the oldest entry in the Queue and remove it or return NULL in case the Queue is empty **/
sBuffer *RetrieveFromQueue(sQueue *queue)
{
if (!queue->active) { return NULL; }
queue->start = (queue->start + 1) % queue->bufferSize;
queue->active--;
return &(queue->data[queue->start]);
}
/** return the oldest entry in the Queue or NULL if the Queue is empty. Does not remove the entry **/
sBuffer *PeakAtQueue(sQueue *queue)
{
if (!queue->active) { return NULL; }
return &(queue->data[queue->start]);
}
/*** Shrinks the oldest entry i the Queue by bytes. Removes the entry if buffer of the oldest entry runs empty*/
void ShrinkInQueue(sQueue *queue, int bytes) {
// cannot remove negative amount of bytes - this is an error case. Ignore it
if (bytes <= 0) return;
// remove the entry if the offset is equal to the buffer size
if (queue->data[queue->start].bytes == bytes) {
DelFromQueue(queue);
return;
};
// this is a partial delete
if (queue->data[queue->start].bytes > bytes) {
//shift the memory by the offset
memmove(queue->data[queue->start].data, queue->data[queue->start].data + bytes, queue->data[queue->start].bytes - bytes);
queue->data[queue->start].bytes = queue->data[queue->start].bytes - bytes;
return;
}
// panic is the are to remove more than we have the buffer
if (queue->data[queue->start].bytes < bytes) {
perror("we wrote more than we had - this should never happen\n");
exit(EXIT_FAILURE);
return;
}
}
/** delete the oldest entry from the queue. Do nothing if the Queue is empty **/
void DelFromQueue(sQueue *queue)
{
if (queue->active > 0) {
queue->start = (queue->start + 1) % queue->bufferSize;
queue->active--;
}
}
/** Stats output on SIGUSR1 **/
static void sigUSR1(int signo) {
fprintf(stderr, "Buffer use: %i (%i/%i), STDOUT: %i PIPE: %i:%i\n", queue.active, queue.maxUse, queue.bufferSize, queue.sWrites, queue.pWrites, queue.drops);
}
/** handle signal for terminating **/
static void sigINT(int signo) {
quit++;
if (quit > 1) exit(EXIT_FAILURE);
}
此版本还有一个（可选）参数，该参数指定要为管道缓冲的块数。我的示例调用现在看起来像这样：
some_process | bftee >(onlineAnalysis.pl > results) 16384 | gzip > raw_data.gz
导致在丢弃发生之前缓冲16384个块。这使用了大约32 MB的内存，但......谁在乎？
当然，在真实环境中我使用命名管道，以便我可以根据需要进行附加和分离。看起来像这样：
mkfifo named_pipe
some_process | bftee named_pipe 16384 | gzip > raw_data.gz &
cat named_pipe | onlineAnalysis.pl > results
此外，该过程对信号做出如下反应： SIGUSR1 - ＆gt;将计数器打印到STDERR SIGTERM，SIGINT - ＆gt;首先退出主循环并将缓冲区刷新到管道，第二个立即终止程序。
也许这可以帮助将来的某个人...... 享受
答案 2 :(得分：8)
但是，这会创建一个不断增长的日志文件，即使在驱动器空间不足之前也不会使用它。
为什么不定期轮换日志？甚至有一个程序可以为你做logrotate。
还有一个系统，用于生成日志消息并根据类型对它们执行不同的操作。它被称为syslog。
你甚至可以将两者结合起来。让您的程序生成系统日志消息，配置syslog以将它们放在文件中并使用logrotate来确保它们不会填满磁盘。
如果事实证明你是在为一个小型嵌入式系统编写而且程序输出很重，那么你可以考虑采用各种技术。
答案 3 :(得分：6)
通常在嵌入式设备上使用的BusyBox可以通过
创建ram缓冲日志syslogd -C
可以填写
logger
并通过
阅读logread
效果很好，但只提供一个全局日志。
答案 4 :(得分：5)
似乎bash <>重定向运算符（3.6.10 Opening File Descriptors for Reading and WritingSee）使得对文件/ fifo的写入以非阻塞方式打开。
这应该有效：
$ mkfifo /tmp/mylog
$ exec 4<>/tmp/mylog
$ myprogram 2>&1 | tee >&4
$ cat /tmp/mylog # on demend
gniourf_gniourf 在#bash IRC频道上提供的解决方案。
答案 5 :(得分：4)
如果您可以在嵌入式设备上安装屏幕，则可以在其中运行“myprogram”并将其分离，并在您想要查看日志时随时重新连接。类似的东西：
$ screen -t sometitle myprogram
Hit Ctrl+A, then d to detach it.
每当您想要查看输出时，请重新附加输出：
$ screen -DR sometitle
Hit Ctrl-A, then d to detach it again.
这样您就不必担心使用磁盘空间的程序输出了。
答案 6 :(得分：3)
给定fifo方法的问题是，当管道缓冲区被填满并且没有进行读取过程时，整个事情将会挂起。
对于fifo工作方法，我认为您必须实现类似于BASH: Best architecture for reading from two input streams中提到的命名管道客户端 - 服务器模型（请参阅下面的略微修改的代码，示例代码2）。
对于解决方法，您还可以使用while ... read构造而不是tee stdout到命名管道，方法是在while ... read循环内部实施计数机制，定期覆盖日志文件按指定的行数。这可以防止日益增长的日志文件（示例代码1）。
# sample code 1
# terminal window 1
rm -f /tmp/mylog
touch /tmp/mylog
while sleep 2; do date '+%Y-%m-%d_%H.%M.%S'; done 2>&1 | while IFS="" read -r line; do
lno=$((lno+1))
#echo $lno
array[${lno}]="${line}"
if [[ $lno -eq 10 ]]; then
lno=$((lno+1))
array[${lno}]="-------------"
printf '%s\n' "${array[@]}" > /tmp/mylog
unset lno array
fi
printf '%s\n' "${line}"
done
# terminal window 2
tail -f /tmp/mylog
#------------------------
# sample code 2
# code taken from:
# https://stackoverflow.com/questions/6702474/bash-best-architecture-for-reading-from-two-input-streams
# terminal window 1
# server
(
rm -f /tmp/to /tmp/from
mkfifo /tmp/to /tmp/from
while true; do
while IFS="" read -r -d $'\n' line; do
printf '%s\n' "${line}"
done </tmp/to >/tmp/from &
bgpid=$!
exec 3>/tmp/to
exec 4</tmp/from
trap "kill -TERM $bgpid; exit" 0 1 2 3 13 15
wait "$bgpid"
echo "restarting..."
done
) &
serverpid=$!
#kill -TERM $serverpid
# client
(
exec 3>/tmp/to;
exec 4</tmp/from;
while IFS="" read -r -d $'\n' <&4 line; do
if [[ "${line:0:1}" == $'\177' ]]; then
printf 'line from stdin: %s\n' "${line:1}" > /dev/null
else
printf 'line from fifo: %s\n' "$line" > /dev/null
fi
done &
trap "kill -TERM $"'!; exit' 1 2 3 13 15
while IFS="" read -r -d $'\n' line; do
# can we make it atomic?
# sleep 0.5
# dd if=/tmp/to iflag=nonblock of=/dev/null # flush fifo
printf '\177%s\n' "${line}"
done >&3
) &
# kill -TERM $!
# terminal window 2
# tests
echo hello > /tmp/to
yes 1 | nl > /tmp/to
yes 1 | nl | tee /tmp/to
while sleep 2; do date '+%Y-%m-%d_%H.%M.%S'; done 2>&1 | tee -a /tmp/to
# terminal window 3
cat /tmp/to | head -n 10
答案 7 :(得分：2)
如果您的进程写入任何日志文件，然后擦除文件并反复重新启动，那么它不会太大，或使用logrotate。
tail --follow=name --retry my.log
你需要的只是。您将获得与终端一样多的回滚功能。
不需要任何非标准。我没有用小日志文件尝试它，但我们所有的日志都像这样旋转，我从来没有注意到松散的线条。
答案 8 :(得分：0)
可以将日志记录定向到UDP套接字。由于UDP是无连接的，因此它不会阻止发送程序。当然，如果接收器或网络跟不上记录，日志将会丢失。
myprogram 2>&1 | socat - udp-datagram:localhost:3333
然后，当您要观察日志记录时：
socat udp-recv:3333 -
还有其他一些很酷的好处，例如能够同时连接多个侦听器或广播到多个设备。
答案 9 :(得分：0)
为了遵循Fabraxia的脚步，我将分享对racic代码的一些小修改。在我的一个用例中，我需要禁止对STDOUT的写操作，因此我添加了另一个参数：swallow_stdout。如果不是不是 0，则将关闭向STDOUT的输出。
由于我不是C编码人员，因此我在阅读代码时添加了注释，也许它们对其他人很有用。
/* ftee - clone stdin to stdout and to a named pipe
(c) racic@stackoverflow
WTFPL Licence */
// gcc /tmp/ftee.c -o /usr/local/bin/ftee
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <signal.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
int readfd, writefd; // read & write file descriptors
struct stat status; // read file descriptor status
char *fifonam; // name of the pipe
int swallow_stdout; // 0 = write to STDOUT
char buffer[BUFSIZ]; // read/write buffer
ssize_t bytes; // bytes read/written
signal(SIGPIPE, SIG_IGN);
if(3!=argc)
{
printf("Usage:\n someprog 2>&1 | %s [FIFO] [swallow_stdout] \n"
"FIFO - path to a named pipe (created beforehand with mkfifo), required argument\n"
"swallow_stdout - 0 = output to PIPE and STDOUT, 1 = output to PIPE only, required argument\n", argv[0]);
exit(EXIT_FAILURE);
}
fifonam = argv[1];
swallow_stdout = atoi(argv[2]);
readfd = open(fifonam, O_RDONLY | O_NONBLOCK); // open read file descriptor in non-blocking mode
if(-1==readfd) // read descriptor error!
{
perror("ftee: readfd: open()");
exit(EXIT_FAILURE);
}
if(-1==fstat(readfd, &status)) // read descriptor status error! (?)
{
perror("ftee: fstat");
close(readfd);
exit(EXIT_FAILURE);
}
if(!S_ISFIFO(status.st_mode)) // read descriptor is not a FIFO error!
{
printf("ftee: %s in not a fifo!\n", fifonam);
close(readfd);
exit(EXIT_FAILURE);
}
writefd = open(fifonam, O_WRONLY | O_NONBLOCK); // open write file descriptor non-blocking
if(-1==writefd) // write file descriptor error!
{
perror("ftee: writefd: open()");
close(readfd);
exit(EXIT_FAILURE);
}
close(readfd); // reading complete, close read file descriptor
while(1) // infinite loop
{
bytes = read(STDIN_FILENO, buffer, sizeof(buffer)); // read STDIN into buffer
if (bytes < 0 && errno == EINTR)
continue; // skip over errors
if (bytes <= 0)
break; // no more data coming in or uncaught error, let's quit since we can't write anything
if (swallow_stdout == 0)
bytes = write(STDOUT_FILENO, buffer, bytes); // write buffer to STDOUT
if(-1==bytes) // write error!
perror("ftee: writing to stdout");
bytes = write(writefd, buffer, bytes); // write a copy of the buffer to the write file descriptor
if(-1==bytes);// ignore errors
}
close(writefd); // close write file descriptor
return(0); // return exit code 0
}