Unix Shell Scripting Tutorial - page 6

Question: How can we search in file using Regular expression?
We use grep command.

grep "search string" filename.txt

Question: How to search a string in file?

grep "search string" filename.txt

search string is text searched in filename.txt. By Default its case sensitive.


Question: How to search a case-insensitive string in file?
use -i to search case insensitive.

grep -i "search string" filename.txt

Question: How to search a string in mutiple file?
separate the filename by space.

grep -i "search string" filename.txt filename2.txt filename3.txt 

Question: How to search a string in file using regular expression? Use regex character for example .* used to search all

grep -i "textname .*" filename.txt 

It will return all after the textname.


Question: What are the basic Regex characters?

1. ? The preceding item is optional and matched at most once.
2. * matched zero or more times.
3. + matched one or more times.
4. {n} matched exactly n times.
5. {n,} matched n or more times.
6. {,m} matched at most m times.
7. {n,m} matched at least n times, but not more than m times.

Question: How to search a words in file?
Use -w to search words.

grep -iw "textname" filename.txt 

It will not search textnameA.


Question: How to search and return next line?

grep -A 3 -i "textname" filename.txt

It will search and return next 3 lines after search.
You can use -B to return Before 3 lines.


Question: How to search recursively in folder? Use -r to search recursive.

grep -r "textname" 

It will search in current folder and sub-folder.


Question: How to find number of matches ? Use -c to return number of matches.

grep -c "textname" fiename.txt

It will return number of matches in number.


Question: What are the Performance Tools in unix?

1. nice/renice: Runs a program with modified scheduling priority.
2. netstat: Prints network connections, routing tables and interface statistics.
3. time: give resource usage
4. uptime: This is System Load Average.
5. ps: Current process list
6. vmstat: Virtual Memory stats
7. top: Top Task List

Question: What is syslog?
Syslog is a way for network devices to send event messages to a server. Also known as Syslog server.
SysLog is stored in /etc/syslogd OR /etc/syslog.

syslog.conf have following configuration.
*.err;kern.debug;auth.notice /dev/console
daemon,auth.notice           /var/log/messages
lpr.info                     /var/log/lpr.log
mail.*                       /var/log/mail.log
ftp.*                        /var/log/ftp.log
mark.*                       /dev/console

Question: What is command for logging?

logger [-i] [-f file] [-p priority] [-t tag] [message]

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Unix Shell Scripting Tutorial - page 5

Question: What are the directory structure of unix?

1. /: This is the root directory which should contain only the directories.
2. /bin: Executable files are located here.
3. /dev: Device drivers
4. /etc: configuration files, valid user lists, groups, ethernet and hosts etc
5. /lib: shared library files and sometimes other kernel-related files.
6. /boot: files for booting the system.
7. /home: home directory for users and other accounts
8. /mnt: Used to mount other temporary file systems like CD/pendrive
9. /proc: Contains all processes marked as a file by process number.
10. /tmp: Holds temporary files used between system boots.
11. /user: Used for miscellaneous purposes.
12. /var: Typically contains log and print files.
13. /sbin: Contains binary (executable) files.
14. /kernel: kernel files

Question: How to create a new Group?

groupadd mynewgroup

Question: How to modify group name?

groupmod -n new_modified_group_name old_group_name

Question: How to delete group?

groupdel new_modified_group_name

Question: How to add a existing user to a group?

usermod -a -G mynewgroup username

-G Its for secondary group.
-g Its for primary group.


Question: How to change a User's Primary Group?

usermod -g groupname username  

Question: How to list groups of loggined user?

groups

Question: How to list groups of other user?

groups username

Question: How to Create a New User and Assign a Group?

useradd -G examplegroup username

Question: How to assign a user multiple groups?

usermod -a -G group1,group2,group3 username

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