为什么我不能将输出从 sed 重定向到文件

问题描述

我正在尝试运行以下命令

I am trying to run the following command

./someprogram | tee /dev/tty | sed 's/^.{2}//' > output_file

但是当我去检查文件时，文件总是空白的.如果我删除 >output_file 从命令末尾，我可以看到 sed 的输出，没有任何问题.

But the file is always blank when I go to check it. If I remove > output_file from the end of the command, I am able to see the output from sed without any issues.

有什么方法可以将此命令中 sed 的输出重定向到文件?

Is there any way that I can redirect the output from sed in this command to a file?

推荐答案

使用 -u 标志从 sed 命令中删除输出缓冲，并确定你想要什么日志不在标准错误上

Remove output-buffering from sed command using the -u flag and make sure what you want to log isn't on stderr

-u, --无缓冲

  load minimal amounts of data from the input files and flush the output buffers more often

最终命令:

./someprogram | tee /dev/tty | sed -u 's/^.{2}//' > output_file

流会发生这种情况(通常是程序在其整个生命周期内将输出发送到标准输出).

This happens with streams (usually a program sending output to stdout during its whole lifetime).

sed/grep 和其他命令在这些情况下会进行一些缓冲，您必须明确禁用它才能在程序仍在运行时进行输出.

sed / grep and other commands do some buffering in those cases and you have to explicitly disable it to be able to have an output while the program is still running.

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