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linux_introduction
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adds basic grep

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waldek 2022-05-09 17:51:12 +02:00
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essential/readme.md
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@ -1545,6 +1545,7 @@ This being said, you can use `grep` without regular expressions as well and this
Most distributions will come with some dictionaries installed.
We can find the American one with the `locate` command.
The *third* one in line is the one we need, but have a look at the other files if you're intrigued.
```
waldek@debian:~$ locate american
@ -1581,6 +1582,51 @@ waldek@debian:~$ locate american
/var/lib/ispell/american.remove
```
We can use `grep` to find all occurrences of the word *hippo* with the following syntax.
```
waldek@debian:~$ grep "hippop" /usr/share/dict/american-english
hippopotami
hippopotamus
hippopotamus's
hippopotamuses
waldek@debian:~$
```
We can search for multiple patterns with the `|` character **but** this charater has a special meaning in the shell so we need to escape it with a `\` **or** we can use *extended* `grep` with either `egrep` or `grep -E`.
```
waldek@debian:~$ grep "hippo\|tamu" /usr/share/dict/american-english
Metamucil
Metamucil's
hippo
hippo's
hippopotami
hippopotamus
hippopotamus's
hippopotamuses
hippos
whippoorwill
whippoorwill's
whippoorwills
waldek@debian:~$ grep -E "hippo|tamu" /usr/share/dict/american-english
Metamucil
Metamucil's
hippo
hippo's
hippopotami
hippopotamus
hippopotamus's
hippopotamuses
hippos
whippoorwill
whippoorwill's
whippoorwills
waldek@debian:~$
```
Adding the `--color` argument to `grep will make the matched patterns jump out with a color, depending on the color scheme of your terminal.
## Wildcards and regular expressions
# Exercise