[英]How to translate this Python code to Node.js
我在这里得到了一个非常好的答案,关于如何清除行/删除文件中的行而不必截断文件或用新版本的文件替换文件,这里是Python代码:
#!/usr/bin/env python
import re,os,sys
logfile = sys.argv[1]
regex = sys.argv[2]
pattern = re.compile(regex)
with open(logfile,"r+") as f:
while True:
old_offset = f.tell()
l = f.readline()
if not l:
break
if pattern.search(l):
# match: blank the line
new_offset = f.tell()
if old_offset > len(os.linesep):
old_offset-=len(os.linesep)
f.seek(old_offset)
f.write(" "*(new_offset-old_offset-len(os.linesep)))
这个脚本可以像:
./clear-line.py <file> <pattern>
出于教育目的,我想弄清楚我是否可以在Node.js中写这个。 我当然可以逐行读取Node.js文件。 但是我不确定在这种情况下Node.js是否具有等效的tell / seek调用。
写作的等价物肯定是
https://nodejs.org/api/fs.html#fs_fs_write_fd_buffer_offset_length_position_callback
这是我的尝试
#!/usr/bin/env node
const readline = require('readline');
const fs = require('fs');
const file = process.argv[2];
const rgx = process.argv[3];
const fd = fs.openSync(file, 'r+');
const rl = readline.createInterface({
input: fs.createReadStream(null, {fd: fd})
});
let position = 0;
const onLine = line => {
position += line.length;
if (String(line).match(rgx)) {
let len = line.length;
rl.close();
rl.removeListener('line', onLine);
// output the line that will be replaced/removed
process.stdout.write(line);
fs.write(fd, new Array(len + 1).join(' '), position, 'utf8', err => {
if (err) {
process.stderr.write(err.stack || err);
process.exit(1);
}
else {
process.exit(0);
}
});
}
};
rl.on('line', onLine);
这不太对 - 我认为我没有正确计算偏移/位置。 也许知道Python和Node的人可以帮助我。 我不太熟悉计算文件中的位置/偏移量,特别是在缓冲区方面。
这是我正在使用的文本文件中的数据。 我想要做的就是读取非空的第一行,然后从文件中删除该行并将该行写入stdout。
这可能是任何非空白数据,但这里是我正在使用的JSON:
{"dateCreated":"2016-12-26T09:52:03.250Z","pid":5371,"count":0,"uid":"7133d123-e6b8-4109-902b-7a90ade7c655","isRead":false,"line":"foo bar baz"}
{"dateCreated":"2016-12-26T09:52:03.290Z","pid":5371,"count":1,"uid":"e881b0a9-8c28-42bb-8a9d-8109587777d0","isRead":false,"line":"foo bar baz"}
{"dateCreated":"2016-12-26T09:52:03.390Z","pid":5371,"count":2,"uid":"065e51ff-14b8-4454-9ae5-b85152cfcb64","isRead":false,"line":"foo bar baz"}
{"dateCreated":"2016-12-26T09:52:03.491Z","pid":5371,"count":3,"uid":"5af80a95-ff9d-4252-9c4e-0e421fd9320f","isRead":false,"line":"foo bar baz"}
{"dateCreated":"2016-12-26T09:52:03.595Z","pid":5371,"count":4,"uid":"961e578f-288b-413c-b933-b791f833c037","isRead":false,"line":"foo bar baz"}
{"dateCreated":"2016-12-26T09:52:03.696Z","pid":5371,"count":5,"uid":"a65cbf78-2ea1-4c3a-9beb-b4bf56e83a6b","isRead":false,"line":"foo bar baz"}
{"dateCreated":"2016-12-26T09:52:03.799Z","pid":5371,"count":6,"uid":"d411e917-ad25-455f-9449-ae4d31c7b1ad","isRead":false,"line":"foo bar baz"}
{"dateCreated":"2016-12-26T09:52:03.898Z","pid":5371,"count":7,"uid":"46f8841d-c86c-43f2-b440-8ab7feea7527","isRead":false,"line":"foo bar baz"}
{"dateCreated":"2016-12-26T09:52:04.002Z","pid":5371,"count":8,"uid":"81b5ce7e-2f4d-4acb-884c-442c5ac4490f","isRead":false,"line":"foo bar baz"}
{"dateCreated":"2016-12-26T09:52:04.101Z","pid":5371,"count":9,"uid":"120ff45d-74e7-464e-abd5-94c41e3cd089","isRead":false,"line":"foo bar baz"}
您应该考虑每行末尾的换行符,该换行符不包含在您通过readline模块获得的“行”中。 也就是说,你应该将position += (line.length + 1)
更新到position += (line.length + 1)
,然后在写入时,只需使用position
(不带-1
)。
好吧,我想我明白了,但是如果有人有这方面的牛肉,请随意批评。 它很接近,但它需要一些微调我认为,似乎有一个一个一个错误或类似的东西。
#!/usr/bin/env node
const readline = require('readline');
const fs = require('fs');
const file = process.argv[2];
const rgx = new RegExp(process.argv[3]);
const fd = fs.openSync(file, 'r+');
const rl = readline.createInterface({
input: fs.createReadStream(null, {fd: fd})
});
let position = 0;
const onLine = line => {
if (String(line).match(rgx)) {
let len = line.length;
rl.close();
rl.removeListener('line', onLine);
// output the line that will be replaced/removed
process.stdout.write(line + '\n');
fs.write(fd, new Array(len + 1).join(' '), position, 'utf8',
(err, written, string) => {
if (err) {
process.stderr.write(err.stack || err);
return process.exit(1);
}
else {
process.exit(0);
}
});
}
position += (line.length + 1); // 1 is length of \n character
};
rl.on('line', onLine);
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