Bash exec命令找不到错误原因分析及Redis容器入口脚本管道输出配置问询

1. Why your test script fails with exec "$CMD" #

That error happens because when you wrap $CMD in quotes, the shell treats the entire string as one single executable name—so it's literally looking for a file called sh -c "echo 123" (spaces and all), which obviously doesn't exist.

When you run sh -c "echo 123" directly in the console, the shell splits the line into separate arguments: sh, -c, "echo 123". But when you store that whole line in a variable and quote it during execution, the shell doesn't do that splitting anymore.

Fixes: #

• Best practice: Use an array (safe for commands with any arguments):

  #!/bin/sh
  CMD=(sh -c "echo 123")
  exec "${CMD[@]}"
  

  Arrays preserve each argument as a separate element, so the shell knows exactly what's the command and what are its parameters.

• Quick fix (less safe): Skip quoting the variable

  #!/bin/sh
  CMD='sh -c "echo 123"'
  exec $CMD
  

  This works here, but be careful—if your command has arguments with spaces or special characters, this will break. Stick to arrays for robustness.

2. Piping Redis output to log-converter in your Docker entrypoint #

The issue with exec sh -c "$@ | log-converter" is that when you expand "$@" into the shell command string, you're not preserving the original arguments correctly. If $@ includes things like flags with spaces, the inner shell will misinterpret them, and the pipe might not behave as expected.

The Correct Fix: #

Replace that line with this:

exec sh -c '$0 "$@" | log-converter' -- "$@"

Let's break this down: #

• sh -c '$0 "$@" | log-converter': This runs a new shell where the command is $0 "$@" | log-converter. The single quotes prevent the outer shell from messing with the variables inside.
• --: This tells the inner shell that the following arguments are not options, so they get assigned to $0, $1, etc.
• "$@": Passes all the original entrypoint arguments (like redis-server and any flags) to the inner shell. Here, $0 becomes redis-server, and "$@" are its arguments—so it runs exactly like the original exec "$@" but pipes the output to log-converter.

Example Integration: #

If your entrypoint script originally had:

# Original line to run Redis
exec "$@"

Swap it with the fixed line, and it will pipe Redis's output through log-converter while maintaining all the original command arguments correctly.

内容的提问来源于stack exchange，提问作者Greyshack