#2166

[Bash] How-To

Olivier | How-To | 15

Create a tar.gz file for each file :

for i in *.dbf; do tar -czf $i.tar.gz $i; done

Add datetime in bash history :

echo 'export HISTTIMEFORMAT="%d/%m/%y %T "' >> ~/.bash_profile

To replace the first occurrence of a pattern with a given string, use ${parameter/pattern/string}:

#!/bin/bash
firstString="I love Suzi and Marry"
secondString="Sara"
echo "${firstString/Suzi/$secondString}"    
# prints 'I love Sara and Marry'

To replace all occurrences, use ${parameter//pattern/string}:

message='The secret code is 12345'
echo "${message//[0-9]/X}"           
# prints 'The secret code is XXXXX'

Show path in bash prompt
Add following line in .bashrc

export PS1="\\u@\\h:\\w\\$ "

Check keyboard input and call associated function:
Script used to ask confirmation before stopping a tomcat instance.

Information like reason, username, datetime are stored in a logfile.

#!/bin/bash

function stopApp(){
	read -p "You are requesting a stop of the application, thanks to provide an explanation : " explanation
	echo `date` "- $USER - " `who am i | awk '{print $1}'` " - Stoping Tomcat... (Reason : $explanation)" >> log.log
	./shutdown.sh
}

while true; do
    read -p "Do you want to stop the application ? (Y/N) : " yn
    case $yn in
        [Yy]* ) stopApp; break;;
        [Nn]* ) exit;;
        * ) echo "Please answer yes or no.";;
    esac
done

trim leading and trailing whitespace :

awk '{$1=$1};1'

#Eaxmple :
ip a | grep inet | grep -v "127.0.0.1" | grep -v "inet6" | awk '{$1=$1};1'

bash, How-to, linux, shell

Setup FileZilla Server Passive Ports on Windows Server 2012 — (B)logs of Johan Dörper Using Zabbix API for Custom Reports – Arturo Baldo

15 thoughts on “[Bash] How-To”

Olivier says:

03/07/2020 at 09:32

Zip a folder :
```
zip -r data.zip data/
```
Reply
Olivier says:

06/07/2020 at 07:16

Check free inodes :
```
df -ih
```
This will take time, but can locate the directory with the most files
```
find . -xdev -type f | cut -d "/" -f 2 | sort | uniq -c | sort -n
```
Reply

OLIVIER COMBE says:

14/10/2020 at 08:32

Retry function :

## ###################################### ##
## Retry function
## ###################################### ##
retry() {
    local -r -i max_attempts="$1"; shift
    local -r cmd="$@"
    local -i attempt_num=1
    until $cmd
    do
        if ((attempt_num==max_attempts))
        then
            echo "Attempt $attempt_num failed and there are no more attempts left!"
            return 1
        else
            echo "Attempt $attempt_num failed! Trying again in ${attempt_num}0 seconds..."
            sleep $((attempt_num++))0
        fi
    done
}

OLIVIER COMBE says:

02/12/2020 at 08:35

Check Defunct process :
```
ps -ef | grep '<defunct>'
```
Kill defunct process (based on parend ID)
```
ps -ef | grep '<defunct>'| grep -v grep | cut -b15-20 | xargs kill -9 
```
Reply
OLIVIER COMBE says:

11/12/2020 at 09:22

Substring by index (1-based)
```
echo "abcdefghi" | cut -c2-6
bcdef
```
```
A="abcdefghi"
echo ${A:0:3}
abc
```
Reply

OLIVIER COMBE says:

11/12/2020 at 09:23

Uppercase :

$ name='fahmida'
$ echo $name
fahmida
$ echo ${name^}
Fahmida
$ echo ${name^^}
FAHMIDA

Lowercase:

$ name='TOTO'
$ echo $name
TOTO
$ echo ${name,}
tOTO
$ echo ${name,,}
toto

OLIVIER COMBE says:

08/01/2021 at 10:35

Browse subdir

LIST_OF_DIRS=`find . -name *.log | cut -d '/' -f -6 | awk '{$1=$1};1' | uniq`
for DIR in $LIST_OF_DIRS
do
    pushd $DIR    
    prefix=`echo $DIR | cut -d '/' -f 2`
    zipLogs /tmp "${prefix}"    
    popd
done

OLIVIER COMBE says:

02/02/2021 at 10:48

Array :

Add element to an arrat

toBePushed=()

toBePushed+=("A")
toBePushed+=("A1")
toBePushed+=("A2")
toBePushed+=("A3")

Loop on array

for i in "${toBePushed[@]}"
do
    echo "Pusing  ${i}"
done

Print array

printf '%s\n' "${toBePushed[@]}"

OLIVIER COMBE says:

04/02/2021 at 15:50

sed :

sed -i 's%/my/oldpath%/my/new/path%g' my_file.txt

OLIVIER COMBE says:

16/03/2021 at 08:25

Remove duplicate from a file :
```
cat my_file.txt | sort | uniq > my_file_uniq.txt
```
Reply
OLIVIER COMBE says:

03/05/2021 at 12:28

Test zip/jar integrity
```
unzip -t MY_FILE.zip
```
Reply
OLIVIER COMBE says:

20/09/2021 at 10:25

see output of unattached process :
```
cat /proc/<PID>/fd/1
```
(tail is not working properly)

Reply
OLIVIER COMBE says:

05/12/2022 at 14:02

list all mount points:
```
findmnt
```
Reply

OLIVIER COMBE says:

04/01/2023 at 08:45

log with color

Yellow

function logYellow {
    YELL='\033[1;33m';NC='\033[0m' # No Color
    DATE=`date "+%Y-%m-%d %T"`
    printf "${YELL}${DATE} - $1${NC} \n"
}

function logGreen {
    GREEN='\033[1;32m';NC='\033[0m' # No Color
    DATE=`date "+%Y-%m-%d %T"`
    printf "${GREEN}${DATE} - $1${NC} \n"
}

OLIVIER COMBE says:

25/01/2024 at 15:52

Using env variable in sed:
```
sed 's@xxx@'"$PWD"'@'
```
Reply

[Bash] How-To

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15 thoughts on “[Bash] How-To”

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