Linux脚本exec重定向问题：如何同时输出到文件与控制台？

Hey, I totally get what you're stuck on here—you want your script's output (both regular messages and errors) to go to a log file and show up in the terminal, but the exec + tee commands you tried only seem to do one or the other. Let's fix this with the right syntax and explain why your previous attempts didn't work.

正确的exec+tee实现方式 #

The correct command to set up global redirection for both stdout and stderr to both terminal and log file is:

exec > >(tee -a "$LOGFILE") 2>&1

Let's break down why this works and what you might have missed before:

• The space between > and >(tee ...) is critical—this is process substitution syntax, which tells bash to create a temporary pipe to the tee command. If you skip the space, the shell misinterprets the command.
• Wrapping "$LOGFILE" in double quotes prevents issues if your log file path has spaces or special characters (always a good habit!).
• 2>&1 redirects stderr to stdout, so error messages get caught by tee too—they'll show up in the terminal and get appended to the log file.

为什么你之前的尝试失败了 #

Let's go through why those commands didn't work:

• exec &> >(tee -a $LOGFILE) 2>&1: The &> already redirects both stdout and stderr to the process substitution. Adding 2>&1 afterward is redundant and can cause the shell to mishandle the file descriptors, leading to only one output stream working.
• exec >> $LOGFILE 2>&1 && tail -f $LOGFILE: The exec command replaces the current shell process—once it runs, the tail -f part never executes. That's why you only get output in the log file, not the terminal.

兼容POSIX shell的替代方案 #

If you're working with a strict POSIX shell (not bash, which supports process substitution by default), the script command is a reliable alternative:

script -a -q "$LOGFILE"

• -a tells script to append to the log file instead of overwriting it.
• -q enables quiet mode, so you don't get extra "Script started/ended" messages cluttering your output.
  After running this, all subsequent commands in the script will output to both the terminal and the log file. To exit the script session (and stop logging), just run exit.

逐命令处理的备选方案 #

If you don't want to set up global redirection, you can pipe individual commands to tee:

# 仅重定向标准输出
echo "Regular output" | tee -a "$LOGFILE"

# 同时重定向标准输出和标准错误
echo "Error message" >&2 | tee -a "$LOGFILE" 2>&1

This is less convenient for full-script logging, but useful if you only need to capture output from specific commands.

验证是否生效 #

To test if it's working, add these lines to your script after setting up the redirection:

echo "This is a test stdout message"
echo "This is a test stderr message" >&2

Run the script, then check both your terminal and the log file—both messages should appear in both places.

内容的提问来源于stack exchange，提问作者Aravind raj