MAN page
man -a useradd |
useradd command in all sections |
man -k passwd | grep 8 |
searching passwd keyword in man page from section 8 |
man 8 useradd |
showing useradd command from section 8 |
man man |
showing man command help |
Hard links, soft links, finding files
ln /etc/hosts myhosts |
create hard links myhosts to /etc/hosts |
ln -s /etc/hosts/ myhosts |
create symbolic links myhosts |
find /etc -name hosts |
Find in /etc files with exact name "hosts" |
find /etc -name "hosts" |
Find in /etc files with "hosts" in its name |
find /etc -name "hosts" -exec cp {} /etc/test/ \; |
Find in /etc file with "hosts" in name and copy it to /etc/test |
find /etc -size +100K 2>/dev/null |
File in /etc files over 100Kb and send error to /dev/null |
grep student /etc/* 2>/dev/null |
Find in /etc files with "student" in content |
grep -l student /etc/* 2>/dev/null |
List only the directories |
find /etc -exec grep -l student {} \; 2>/dev/null; cp {} /find/contents/ \; 2>/dev/null |
Find all directories and sub with files containing student in content and copy the result to /find/content |
Administrative Tasks
visudo |
Edit sudo configuration file |
chvt t |
Change virtual terminal 5 |
/etc/securetty |
Secure console file, delete 1 will no longer have access to that console |
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Input Output Redirection
> |
overwrite |
< |
send into command |
>> |
append |
<< |
append into command or file |
2> /dev/null |
redirect error to null file |
Text Processing Utilities
cut -d : -f 3 /etc/passwd |
Display third column using ":" delimiter in /etc/passwd |
cut -d : -f 1 /etc/passwd | sort | tr [:lowercase:] [:uppercase:] |
Display all username in /etc/passwd and translate all lowercase to uppercase |
awk -F : ' { print $1 } ' /etc/passwd |
Display first column using ":" field delimiter (-F) |
sed -i -e '10d' grepfile1 |
Delete (10d) interactively (-i) using edit option(-e) the tenth line |
Archive, Backup, Compress, Uncompress
tar cvf name.tar /dir |
Create name.tar file from /dir |
tar -xvfz archive.tar.gzip -C /target/dir |
Extract archive.tar.gzip to /tar/dir |
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Create, Delete, Copy, Move
ls -al /etc |
list all files (-a) with all info (-l) in /etc |
ls -r |
list sub-directories (-r) |
cp -R /etc/hosts ~/files/ |
copy all (-R) in hosts to home/files/ |
mkdir -p /etc/photos |
make directory etc and sub-directory photos |
mv /tmp/test ~ |
move test to home directory |
rm -rf |
remove recursively and ignore non existent file |
head, tail,
head -n 5 /etc/passwd |
Display first 5 lines in /etc/passwd |
tail -f /var/log/messages |
Display the recent system messages |
Regular expressions
note |
Use with sed, vim, awk, grep |
^ |
Start of a string |
^abc |
abc, abcdef,abc123 |
$ |
End of a string |
abc$ |
abc,123abc,fdeabc |
| |
Alteration |
1|8 |
1,8 |
{...} |
Exact quanity |
ab{2}c |
abbc |
[...] |
Explicit set of character to match |
a[bB]c |
abc,aBc |
* |
Null or more of the preceding character |
ab*c |
ac,abc,abbbbc |
(...) |
Group of character |
(123){3} |
123123123 |
+ |
One or more of predceding character |
ab+c |
abc,abbbbc |
? |
Null or 1 of the preceding character |
ab?c |
abc, ac |
. |
Any single character |
\s |
Whitespaces |
.* |
Zero or more of any character |
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