bash 在一个命令中创建临时文件并将输出重定向到它
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Create temporary file and redirect output to it in one command
提问by Travis Clarke
I designed a custom script to grep a concatenated list of .bash_historybackup files. In my script, I am creating a temporary file with mktempand saving it to a variable temp. Next, I am redirecting output to that file using the catcommand.
我设计了一个自定义脚本来 grep.bash_history备份文件的连接列表。在我的脚本中，我正在创建一个临时文件mktemp并将其保存到变量temp. 接下来，我使用cat命令将输出重定向到该文件。
Is there a means to create a temporary file (using mktemp), redirect output to it, then store it in a variable in one command, while preserving newline characters?
有没有办法创建一个临时文件（使用mktemp），将输出重定向到它，然后在一个命令中将它存储在一个变量中，同时保留换行符？
The below snippet of code works just fine, but I have a feeling there is a more terse and canonical way to achieve this in one line – maybe using process substitutionor something of the like.
下面的代码片段工作得很好，但我觉得有一种更简洁、更规范的方法可以在一行中实现这一点——可能使用进程替换或类似的方法。
# Concatenate all .bash_history files into a temporary file `temp`.
temp="$(mktemp)"
cat "$HOME/.bash_history."* > $temp
trap 'rm -f $temp' 0
# Set `HISTFILE` shell variable to the `temp` file.
HISTFILE="$temp"
keyword=""
# Search for `keyword` using the `history` command
if [[ "$keyword" ]]; then
# Enable history
set -o history
history | grep "$keyword"
# Disable history
set +o history
else
echo -e "usage: search <keyword>"
exit 0
fi
回答by Charles Duffy
If you're comfortable with the side effect of making the assignment conditional on tempfilenot previously having a nonempty value, this is straightforward via the ${var:=value}expansion:
如果您对使赋值以tempfile先前没有非空值为条件的副作用感到满意，那么通过${var:=value}扩展可以很简单：
cat "$HOME/.bash_history" >"${tempfile:=$(mktemp)}"
回答by artdanil
I guess there is more than one way to do it. I found following to be working for me:
我想有不止一种方法可以做到这一点。我发现以下对我有用：
cat myfile.txt > $(echo "$(mktemp)")
Also don't forget about tee:
也不要忘记tee：
cat myfile.txt | tee "$(mktemp)" > /dev/null
