英文:
Bash script to redirect avoid terminal output after few seconds
问题
我想编写一个脚本，它可以执行另一个bash脚本，然后在执行几秒钟后将脚本的输出重定向到终端之外的文件，以防止初始执行后将不必要的输出打印到屏幕上。
让我们将这个脚本命名为process.sh。我想编写类似以下的内容：
#!/bin/bash
process.sh & # 进程必须在后台运行，因为终端必须保持空闲以供其他进程使用
(sleep 5s
exec 1> cache_file) &
注意：上述脚本中有一些问题，可能需要根据你的需求进行调整，以确保它按预期工作。
英文:
I want to write a script which executes another bash script, and then redirects the script's output to the terminal after a few seconds of execution to a file instead, preventing unnecessary output being printed to the screen after initial execution.
Let's name the script process.sh. I want to write something like
!#/bin/bash
process.sh & # process will have to run in background
# since terminal has to be kept free for other processes
(sleep 5s
exec 1> cache_file) &
答案1
得分: 1
尝试这段经过 Shellcheck 清理的代码：
#!/bin/bash -p
kINIT_DURATION=5 # 秒
kOUTPUT_FILE=cache_file
./process.sh | {
start_time=$SECONDS
init_end_time=$((start_time + kINIT_DURATION))
while IFS= read -r line || [[ -n $line ]]; do
printf '%s\n' "$line"
if (( SECONDS > init_end_time )); then
cat >"$kOUTPUT_FILE"
exit
fi
done
}
- 请查看 BashFAQ/001 (如何逐行（和/或逐字段）读取文件（数据流、变量）？) 以了解
while IFS= read -r line ...循环的解释，该循环读取来自process.sh的输出，包括[[ -n $line ]]测试以处理可能未终止的最后一行输出。 - 使用纯 Bash 代码逐行读取输入速度较慢，特别是当输入来自管道时（因为它必须逐字符读取以确保不读取行尾之外的字符）。如果
process.sh生成大量输出，这段代码可能会太慢。 - Bash 字符串无法包含 ASCII NUL 字符，因此如果
process.sh生成包含它们的输出，该代码将无法正常工作。基本上，它只适用于文本，而不适用于二进制数据。
英文:
Try this Shellcheck-clean code:
#! /bin/bash -p
kINIT_DURATION=5 # seconds
kOUTPUT_FILE=cache_file
./process.sh | {
start_time=$SECONDS
init_end_time=$((start_time + kINIT_DURATION))
while IFS= read -r line || [[ -n $line ]]; do
printf '%s\n' "$line"
if (( SECONDS > init_end_time )); then
cat >"$kOUTPUT_FILE"
exit
fi
done
}
- See BashFAQ/001 (How can I read a file (data stream, variable) line-by-line (and/or field-by-field)?) for an explanation of the
while IFS= read -r line ...loop that reads the output fromprocess.sh, including the[[ -n $line ]]test to deal with a possibly unterminated final line of output. - Reading input line-by-line is slow with pure Bash code. It is particularly slow when input is from a pipeline (because it has to read character-by-character to ensure that it doesn't read past the ends of lines). This code may be too slow if
process.shgenerates a lot of output. - Bash strings can't hold ASCII NUL characters, so the code won't work if
process.shgenerates output that contains them. Essentially, it only works for text, not binary, data.
答案2
得分: 0
If you're happy to log all output, not just after 5 seconds:
#!/bin/bash
nohup process.sh </dev/null 1>out.log 2>err.log &
tail -n +1 -f out.log &
sleep 5
kill $!
英文:
If you're happy to log all output, not just after 5 seconds:
#!/bin/bash
nohup process.sh </dev/null 1>out.log 2>err.log &
tail -n +1 -f out.log &
sleep 5
kill $!
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