Useful commands in Linux for specific tasks

Below are the few commands which were useful during my tasks in linux. There are so many challenges we face during our work and we always come with a solution at last. So it is good to spread that solution to everyone.

I always try to note down them in my documents. Now i will post them here in this blog.

1) RSYNC FOR LOCAL FOLDERS

1	rsync -rtvu uploads-bkp-26082016/ uploads/

Where

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-r - recursive -t - to save modified timestamp -v - verbose -u - do not overwrite existing files in destination folder untill the file modification time changed in source folder.

2) FIND COMMAND TO SEARCH FILES FOR MULTIPLE EXTENSIONS  AND FOR SINGLE FOLDER NOT RECURSIVELY

1	find /app/ -maxdepth 1 -iname '*.tar.gz' -o -name '*.sql'

AND FILES OLDER THEN n DAYS WITHOUT RECURSIVE SEARCH

1	find /app/ -maxdepth 1 -type f -mtime +n

3) Script to Automate document Root and also for the sql database with logging

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#!/bin/bash # ------------------------------------------------------------------------- # Prerequisites Variables DB_HOST="xyz.com" DB_USER='user' DB_PASS='password' DB_NAME='db_name' BACKUP_DIR='/backup' LOG_DIR='/backup/logs'   echo "############################" >> $LOG_DIR/backup.log echo `date`  >> $LOG_DIR/backup.log echo "############################" >> $LOG_DIR/backup.log   #website folder backup tar -zcvf $BACKUP_DIR/backup_name-`date +%d%b%Y-%HH`.tar.gz  /data_folder   > /dev/null   if [ $? -eq 0 ] then tar -zcvf $BACKUP_DIR/httpd-`date +%d%b%Y-%HH`.tar.gz /etc/httpd     ## Apache dir backup   mysqldump -h $DB_HOST -u $DB_USER $DB_NAME -p`$DB_PASS` > $BACKUP_DIR/db-`date +%d%b%Y-%HH`.sql     if [ $? -eq 0 ] then     echo "`date`| DB backup done successfully.." >> $LOG_DIR/backup.log else         echo "`date`| DB backup failed.." >>  $LOG_DIR/backup.log     fi   fi

4) How to print options fields for user 

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PS3='Please enter your choice: ' echo $PS3 options=("Name" "Age" "Lname" "Quit") select opt in "${options[@]}" do     case $opt in         "Name")             echo "you chose choice 1"             ENV_VAR=test             echo $ENV_VAR             break             ;;         "Age")             echo "you chose choice 2"             ;;         "Lname")             echo "you chose choice 3"             ;;         "Quit")             break             ;;         *) echo invalid option;;     esac done

5) Flush home page cache from varnish in magento website.

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varnishadm ban.url '^/(?:index.php?)?$'   OR   try this if required   varnishadm ban.url '^/(?:http:\/\/www.domain.com.au?)?$'

or if you want to flush any other specific url then replace index.php to your URL.

6) How to pass password in ssh command to remote server along with multiple commands with sudo user?

1	sshpass -p 'passwd' ssh -t user@ip "echo passwd | sudo -S cmd1 && cmd2"

Here

-p -> for asking password with sshpass – insecure method to pass password which will be visible to everyone in ps command

or

-e -> for this option we need to set ENV varibale “SSHPASS” for password

-S -> for standard input.

7) Merge two files and create a new file with complete sorted content.

1	diff -DVERSION1 file1   file2 | grep -v "#ifndef VERSION1" | grep -v "else" | grep -v "endif" > file3

8) Command to get hists per hour from apache access logs.

1	grep "15/Dec" apache-access_log | cut -d[ -f2 | cut -d] -f1 | awk -F: '{print $2":00"}' | sort -n | uniq -c

Will update this post later with more commands.