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Filter a log file by matching multiple regular expressions

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Filter a log file by matching multiple regular expressions

Better queries, added filter_map etc.

Ran through rustfmt, added another regex
This commit is contained in:
Vsevolod Zubarev 2017-07-19 18:56:08 +03:00
parent fad366bca4
commit e8aa408a38
2 changed files with 62 additions and 0 deletions
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60
src/basics.md
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@ -9,6 +9,7 @@
| [Generate random numbers with normal distribution][ex-rand-dist] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
| [Generate random values of a custom type][ex-rand-custom] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
| [Run an external command and process stdout][ex-parse-subprocess-output] | [![regex-badge]][regex] | [![cat-os-badge]][cat-os] [![cat-text-processing-badge]][cat-text-processing] |
| [Filter a log file by matching multiple regular expressions][ex-regex-filter-log] | [![regex-badge]][regex] | [![cat-text-processing-badge]][cat-text-processing]
| [Declare lazily evaluated constant][ex-lazy-constant] | [![lazy_static-badge]][lazy_static] | [![cat-caching-badge]][cat-caching] [![cat-rust-patterns-badge]][cat-rust-patterns] |
| [Maintain global mutable state][ex-global-mut-state] | [![lazy_static-badge]][lazy_static] | [![cat-rust-patterns-badge]][cat-rust-patterns] |
| [Access a file randomly using a memory map][ex-random-file-access] | [![memmap-badge]][memmap] | [![cat-filesystem-badge]][cat-filesystem] |
@ -270,6 +271,62 @@ fn run() -> Result<()> {
# quick_main!(run);
```
[ex-regex-filter-log]: #ex-regex-filter-log
<a name="ex-regex-filter-log"></a>
## Filter a log file by matching multiple regular expressions
[![regex-badge]][regex] [![cat-text-processing-badge]][cat-text-processing]
Reads a file named `application.log` and only outputs the lines
containing “version X.X.X”, some IP address followed by port 443
(e.g. “192.168.0.1:443”), or a specific warning.
A [`regex::RegexSet`] is built with [`regex::RegexSetBuilder`].
Since backslashes are very common in regular expressions, using
[raw string literals] make them more readable.
```rust,no_run
# #[macro_use]
# extern crate error_chain;
extern crate regex;
use std::fs::File;
use std::io::{BufReader, BufRead};
use regex::RegexSetBuilder;
# error_chain! {
# foreign_links {
# Io(std::io::Error);
# Regex(regex::Error);
# }
# }
#
fn run() -> Result<()> {
let log_path = "application.log";
let buffered = BufReader::new(File::open(log_path)?);
let set = RegexSetBuilder::new(&[
r#"version "\d\.\d\.\d""#,
r#"\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}:443"#,
r#"warning.*timeout expired"#,
]).case_insensitive(true)
.build()?;
let filtered = buffered
.lines()
.filter_map(|line| line.ok())
.filter(|line| set.is_match(line.as_str()));
for line in filtered {
println!("{}", line);
}
Ok(())
}
#
# quick_main!(run);
```
[ex-lazy-constant]: #ex-lazy-constant
<a name="ex-lazy-constant"></a>
## Declare lazily evaluated constant
@ -523,6 +580,8 @@ fn main() {
[`Rng::gen_range`]: https://doc.rust-lang.org/rand/rand/trait.Rng.html#method.gen_range
[`rand::Rand`]: https://doc.rust-lang.org/rand/rand/trait.Rand.html
[`Regex`]: https://doc.rust-lang.org/regex/regex/struct.Regex.html
[`regex::RegexSet`]: https://doc.rust-lang.org/regex/regex/struct.RegexSet.html
[`regex::RegexSetBuilder`]: https://doc.rust-lang.org/regex/regex/struct.RegexSetBuilder.html
[`Output`]: https://doc.rust-lang.org/std/process/struct.Output.html
[`Command`]: https://doc.rust-lang.org/std/process/struct.Command.html
[`HashMap`]: https://doc.rust-lang.org/std/collections/struct.HashMap.html
@ -535,3 +594,4 @@ fn main() {
<!-- Reference -->
[race-condition-file]: https://en.wikipedia.org/wiki/Race_condition#File_systems
[raw string literals]: https://doc.rust-lang.org/reference/tokens.html#raw-string-literals

2
src/intro.md
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@ -27,6 +27,7 @@ community. It needs and welcomes help. For details see
| [Generate random numbers with normal distribution][ex-rand-dist] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
| [Generate random values of a custom type][ex-rand-custom] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
| [Run an external command and process stdout][ex-parse-subprocess-output] | [![regex-badge]][regex] | [![cat-os-badge]][cat-os] [![cat-text-processing-badge]][cat-text-processing] |
| [Filter a log file by matching multiple regular expressions][ex-regex-filter-log] | [![regex-badge]][regex] | [![cat-text-processing-badge]][cat-text-processing]
| [Declare lazily evaluated constant][ex-lazy-constant] | [![lazy_static-badge]][lazy_static] | [![cat-caching-badge]][cat-caching] [![cat-rust-patterns-badge]][cat-rust-patterns] |
| [Maintain global mutable state][ex-global-mut-state] | [![lazy_static-badge]][lazy_static] | [![cat-rust-patterns-badge]][cat-rust-patterns] |
| [Access a file randomly using a memory map][ex-random-file-access] | [![memmap-badge]][memmap] | [![cat-filesystem-badge]][cat-filesystem] |
@ -251,6 +252,7 @@ Keep lines sorted.
[ex-rand-range]: basics.html#ex-rand-range
[ex-random-port-tcp]: net.html#ex-random-port-tcp
[ex-rayon-iter-mut]: concurrency.html#ex-rayon-iter-mut
[ex-regex-filter-log]: basics.html#ex-regex-filter-log
[ex-rest-custom-params]: net.html#ex-rest-custom-params
[ex-rest-get]: net.html#ex-rest-get
[ex-rest-head]: net.html#ex-rest-head