Unix on Raveen Kumar

Grep for files that does not contain a specific string

Tue, 09 May 2023 00:00:00 +0000

Another useful way to use grep is for printing file names that do not contain a specific string, for example

grep -L "string" *

You can use the -L option of the grep command, which prints the names of all files that do not contain the specified search string.

The * at the end tells grep to search all files in the current directory. If you want to search only specific files or directories, you can replace the * with the filenames or directory names.

Periodically run a program and watch the output

Fri, 05 May 2023 00:00:00 +0000

watch

Execute a program periodically, showing output fullscreen

Example

watch ls

alternative - viddy

Horizontally print file contents

Wed, 03 May 2023 00:00:00 +0000

To concatenate the contents of a vertical file horizontally in Unix, you can use the paste command with the -s option.

Here’s an example:

Let’s say you have a file file.txt with the following vertical content:

apple
banana
orange

You can concatenate the contents horizontally using the following command:

paste -s file.txt

This will produce the output:

apple   banana  orange

The -s option tells paste to concatenate the lines horizontally instead of vertically. By default, paste separates the columns with a tab character. If you want to use a different separator, you can specify it with the -d option followed by the separator character. For example:

Cat

Sat, 18 Feb 2023 00:00:00 +0000

Join multimedia files

cat movie.mpeg.0* > movie.mpeg
cat *mp3 > combined.mp3

bc

Fri, 17 Feb 2023 00:00:00 +0000

bc as a hex calculator

obase=16
ibase=16
9+1

bc fractional

scale=10
1/3

Evaluating expressions from commandline

bc <<< "ibase=10; obase=16; $(grep cru_spare -r | awk -F "," '{print $NF}')"

Diff

Fri, 17 Feb 2023 00:00:00 +0000

To diff 2 files

diff file1 file2

To diff 2 files and view side by side

diff -y file1 file2

Example pstree command

Fri, 17 Feb 2023 00:00:00 +0000

pstree -u username -hp

Linux notes general

Fri, 17 Feb 2023 00:00:00 +0000

Commands

cat - contatenate
tac - concatenate in reverse

`column` command

The column utility formats its input into multiple columns.

printf "a:b:c\n1::3\n" | column -t -s ':'

a	b	c
1	3

Note that this output is different from one that is printed in terminal. Strange… Below is the terminal output.

a	b	c
1		3

`uuidgen` universal unique id generator

Generate unique ID’s

`script` Records terminal

man script
man scriptreplay

Example

script --timing=file.tm script.out
# Write some scripts
# Exit with `exit` or `^d`
scriptreplay --timing file.tm --typescript script.out

`reset` Recover a borked terminal

Count number of files in a directory

ls -1 | wc -l

Building from source

./configure
./configure --prefix=$path

Redirections

2>&1
2>&1 > /dev/null
>
>/dev/null
>>

Keymaps

Ctrl-c
Ctrl-d
Ctrl-l

Readline

C-x C-e to edit current commant in default text editor
or v in vi mode

`ldd` Print shared libraries

This command can be used to find all the shared library or libraries of a program

Unix find

Fri, 17 Feb 2023 00:00:00 +0000

To exclude files or perform reverse match

find . -not -iname "file"

To perform regex matching

find . -regex ".*file"

To find and print only symbolic links in a directory and its subdirectories

find . -type l -print

How to change hostname

Tue, 13 Sep 2022 00:00:00 +0000

How to change hostname

Print hostname

hostname
hostname -I
echo $HOSTNAME

To change hostname

sudo hostname -b <New name>
sudo echo <new name> /etc/hostname

change name in /etc/hosts
If you are in wsl, add the following entry to /etc/wsl.conf

[network]
generateHosts = false

Restart computer

Unix on Raveen Kumar

Grep for files that does not contain a specific string

Periodically run a program and watch the output

watch

Horizontally print file contents

Cat

Join multimedia files

bc

bc as a hex calculator

bc fractional

Evaluating expressions from commandline

Diff

To diff 2 files

To diff 2 files and view side by side

Example pstree command

Linux notes general

Commands

column command

uuidgen universal unique id generator

script Records terminal

Example

reset Recover a borked terminal

Count number of files in a directory

Building from source

Redirections

Keymaps

Readline

ldd Print shared libraries

Unix find

To exclude files or perform reverse match

To perform regex matching

To find and print only symbolic links in a directory and its subdirectories

How to change hostname

How to change hostname

Print hostname

To change hostname

`column` command

`uuidgen` universal unique id generator

`script` Records terminal

`reset` Recover a borked terminal

`ldd` Print shared libraries