Find text in a file/files. The grep command searches through many files at a time to find a piece of text you are looking for.
grep PATTERN [FILE]
$ grep failed transaction.log
The above command will find all of the words in the files that matched the word ‘failed’.
![](https://www.devopsschool.com/blog/wp-content/uploads/2022/09/linux-grep-command-regular-expression-3-1024x329.jpg)
![](https://www.devopsschool.com/blog/wp-content/uploads/2022/09/linux-grep-command-regular-expression-2.jpg)
grep command reference and example
- https://www.devopsschool.com/commands/tools/linux/grep
- https://www.devopsschool.com/blog/unix-command-grep/
28 man grep
29 clear
30 ls
31 more yum.log
32 more dmesg.old
33 clear
34 grep BIOS dmesg.old
35 clear
36 ls
37 grep -R error .
38 clear
39 grep -R -i error .
40 clear
41 grep -R -i error .
42 grep -R -i error . | grep -v BERT
49 grep error dmesg
50 grep error dmesg dmesg.old
51 grep error dmesg dmesg.old messages
52 grep -R -i error .
54 grep error dmesg
55 grep -i error dmesg
56 cd
57 ls
58 ls /var/log/ | grep -i error
59 ls /var/log/ | grep *.log
60 ls /var/log/ | grep .log
61 ls /var/log/ | grep .log | grep -v yum
62 cd /var/log/
63 ls
64 clear
65 grep -o error dmesg
66 grep -o Error dmesg
67 grep Error dmesg
68 grep -n Error dmesg
69 grep -c error .
70 grep -c error
71 grep -c error *
72 grep -c -i error *
![](https://www.devopsschool.com/blog/wp-content/uploads/2022/09/linux-grep-command-regular-expression-1-1024x638.jpg)
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