bash 在linux脚本中有条件地添加或附加到文件
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Conditionally add or append to a file in linux script
提问by Jim
I need to modify a file via a script.
I need to do the following:
IF a specific string does NOT exist then append it.
我需要通过脚本修改文件。
我需要执行以下操作：
如果特定字符串不存在，则附加它。
So I created the following script:
所以我创建了以下脚本：
#!/bin/bash
if grep -q "SomeParameter A" "./theFile"; then
echo exist
else
echo doesNOTexist
echo "# Adding parameter" >> ./theFile
echo "SomeParameter A" >> ./theFile
fi
This works but I need to make some improvements.
I think it would be better if I checked if "SomeParameter" exists and then see if it is followed by "A" or "B". If it is "B" then make it "A".
Otherwise append the string (like I do) BUT BEFORE the start of the last block of comments.
How could I do this?
I am not good in scripting.
Thanks!
这有效，但我需要进行一些改进。
我认为如果我检查“SomeParameter”是否存在，然后查看它后面是“A”还是“B”会更好。如果是“B”，则将其设为“A”。
否则在最后一个注释块开始之前附加字符串（像我一样）。
我怎么能这样做？
我不擅长脚本。
谢谢！
回答by l0b0
First, change any SomeParameterlines if they already exist. This should work with lines like SomeParameteror SomeParameter B, with any number of extra spaces:
首先，更改任何SomeParameter已存在的行。这应该适用于像SomeParameter或这样的行SomeParameter B，带有任意数量的额外空格：
sed -i -e 's/^ *SomeParameter\( \+B\)\? *$/SomeParameter A/' "./theFile"
Then add the line if it doesn't exist:
如果它不存在，则添加该行：
if ! grep -qe "^SomeParameter A$" "./theFile"; then
echo "# Adding parameter" >> ./theFile
echo "SomeParameter A" >> ./theFile
fi
回答by Vijay
awk 'BEGIN{FLAG=0}
/parameter a/{FLAG=1}
END{if(flag==0){for(i=1;i<=NR;i++){print}print "adding parameter#\nparameter A#"}}' your_file
BEGIN{FLAG=0}-initializing a flag variable before the start of the file processing.
BEGIN{FLAG=0}- 在文件处理开始之前初始化标志变量。
/parameter a/{FLAG=1}-setting the flag if the parameter is found in the file.
/parameter a/{FLAG=1}- 如果在文件中找到参数，则设置标志。
END{if(flag==0){for(i=1;i<=NR;i++){print}print "adding parameter#\nparameter A#"}}-finally adding the lines at the end of the file
END{if(flag==0){for(i=1;i<=NR;i++){print}print "adding parameter#\nparameter A#"}}- 最后在文件末尾添加行
回答by Nahuel Fouilleul
A perl one-liner
一个 perl 单行
perl -i.BAK -pe 'if(/^SomeParameter/){s/B$/A/;$done=1}END{if(!$done){print"SomeParameter A\n"}} theFile
a backup theFile.BAK will be created (-i option). A more verbose version, which takes into account the last comments, to be tested. Should be saved in a text file and executed perl my_script.plor chmod u+x my_script.pl./my_script.pl
将创建备份 theFile.BAK（-i 选项）。一个更详细的版本，它考虑到了最后的评论，有待测试。应保存在文本文件中并执行perl my_script.pl或chmod u+x my_script.pl./my_script.pl
#!/usr/bin/perl
use strict;
use warnings;
my $done = 0;
my $lastBeforeComment;
my @content = ();
open my $f, "<", "theFile" or die "can't open for reading\n$!";
while (<$f>) {
my $line = $_;
if ($line =~ /^SomeParameter/) {
$line =~ s/B$/A/;
$done = 1;
}
if ($line !~ /^#/) {
$lastBeforeComment = $.
}
push @content, $line;
}
close $f;
open $f, ">", "theFile.tmp" or die "can't open for writting\n$!";
if (!$done) {
print $f @content[0..$lastBeforeComment-1],"SomeParameter A\n",@content[$lastBeforeComment..$#content];
} else {
print $f @content;
}
close $f;
once it is ok then add the following:
一旦确定，然后添加以下内容：
rename "theFile.tmp", "theFile"
