我如何在这里写一个文档到Bash脚本文件?
当前回答
我喜欢这种方法,因为它简洁、易读,而且在缩进的脚本中表现得很好:
<<-End_of_file >file
→ foo bar
End_of_file
其中→为制表符。
其他回答
我喜欢这种方法,因为它简洁、易读,而且在缩进的脚本中表现得很好:
<<-End_of_file >file
→ foo bar
End_of_file
其中→为制表符。
当需要root权限时
当目标文件需要root权限时,使用|sudo tee而不是>:
cat << 'EOF' |sudo tee /tmp/yourprotectedfilehere
The variable $FOO will *not* be interpreted.
EOF
cat << "EOF" |sudo tee /tmp/yourprotectedfilehere
The variable $FOO *will* be interpreted.
EOF
对于那些寻找纯bash解决方案(或需要速度)的人来说,这里有一个简单的解决方案,没有cat:
# here-doc tab indented
{ read -r -d '' || printf >file '%s' "$REPLY"; } <<-EOF
foo bar
EOF
或简单的“mycat”函数(并避免在环境中留下REPLY):
mycat() {
local REPLY
read -r -d '' || printf '%s' "$REPLY"
}
mycat >file <<-EOF
foo bar
EOF
快速比较“mycat”vs OS cat(1000循环>/dev/null在我的OSX笔记本电脑上):
mycat:
real 0m1.507s
user 0m0.108s
sys 0m0.488s
OS cat:
real 0m4.082s
user 0m0.716s
sys 0m1.808s
注意:mycat不处理文件参数,它只处理“将heredoc写入文件”的问题。
注意:
以下是本主题中其他答案的浓缩和组织,尤其是Stefan Lasiewski和Serge Stroobandt的优秀作品 Lasiewski和我推荐高级bash脚本编写指南中的Ch 19 (Here Documents)
问题(如何在bash脚本中将here文档(又名heredoc)写入文件?)有(至少)3个主要的独立维度或子问题:
要覆盖现有文件、追加到现有文件还是写入新文件? 您的用户或其他用户(例如root)拥有该文件吗? 您是想按字面意思写heredoc的内容,还是让bash在heredoc内解释变量引用?
(还有其他我认为不重要的方面/子问题。考虑编辑这个答案来添加它们!)下面是上面列出的问题的一些更重要的维度组合,使用各种不同的分隔标识符——关于EOF没有什么神圣的,只要确保你用作分隔标识符的字符串没有出现在你的heredoc中:
To overwrite an existing file (or write to a new file) that you own, substituting variable references inside the heredoc: cat << EOF > /path/to/your/file This line will write to the file. ${THIS} will also write to the file, with the variable contents substituted. EOF To append an existing file (or write to a new file) that you own, substituting variable references inside the heredoc: cat << FOE >> /path/to/your/file This line will write to the file. ${THIS} will also write to the file, with the variable contents substituted. FOE To overwrite an existing file (or write to a new file) that you own, with the literal contents of the heredoc: cat << 'END_OF_FILE' > /path/to/your/file This line will write to the file. ${THIS} will also write to the file, without the variable contents substituted. END_OF_FILE To append an existing file (or write to a new file) that you own, with the literal contents of the heredoc: cat << 'eof' >> /path/to/your/file This line will write to the file. ${THIS} will also write to the file, without the variable contents substituted. eof To overwrite an existing file (or write to a new file) owned by root, substituting variable references inside the heredoc: cat << until_it_ends | sudo tee /path/to/your/file This line will write to the file. ${THIS} will also write to the file, with the variable contents substituted. until_it_ends To append an existing file (or write to a new file) owned by user=foo, with the literal contents of the heredoc: cat << 'Screw_you_Foo' | sudo -u foo tee -a /path/to/your/file This line will write to the file. ${THIS} will also write to the file, without the variable contents substituted. Screw_you_Foo
对于将来可能遇到这个问题的人,下面的格式是有效的:
(cat <<- _EOF_
LogFile /var/log/clamd.log
LogTime yes
DatabaseDirectory /var/lib/clamav
LocalSocket /tmp/clamd.socket
TCPAddr 127.0.0.1
SelfCheck 1020
ScanPDF yes
_EOF_
) > /etc/clamd.conf