To work on Linux platform, you cannot avoid using shell commands to complete some tasks. These tasks can be as simple as list files in some directories or find some text in some file, or can be as complex as monitoring processes. In this post, we will share 37 powerful Linux shell commands.
| Task | Commands | |
| 1 | Delete file with 0 byte(empty file) | find . -type f -size 0 -exec rm -rf {} \; find . type f -size 0 -delete |
| 2 | Check process memory consumption | ps -e -o "%C : %p : %z : %a"|sort -k5 -nr |
| 3 | Check process CPU utilizetion | ps -e -o "%C : %p : %z : %a"|sort -nr |
| 4 | Print URLs in cache | grep -r -a jpg /data/cache/* | strings | grep "http:" | awk -F'http:' '{print "http:"$2;}' |
| 5 | Check concurrent http connections and TCP connectio status | netstat -n | awk '/^tcp/ {++S[$NF]} END {for(a in S) print a, S[a]}' |
| 6 | Replace no with yes in a line which contains Root in a file | sed -i '/Root/s/no/yes/' /etc/ssh/sshd_config |
| 7 | Kill mysql process | ps aux |grep mysql |grep -v grep |awk '{print $2}' |xargs kill -9 killall -TERM mysqld kill -9 `cat /usr/local/apache2/logs/httpd.pid` |
| 8 | List service in rc.d | ls /etc/rc3.d/S* |cut -c 15- |
| 9 | Display multiline information with EOF | cat << EOF +--------------------------------------------------------------+ | === Welcome to Tunoff services === | +--------------------------------------------------------------+ EOF |
| 10 | Use of for loop | cd /usr/local/mysql/bin for i in * do ln /usr/local/mysql/bin/$i /usr/bin/$i done |
| 11 | Get IP address | ifconfig eth0 |grep "inet addr:" |awk '{print $2}'|cut -c 6- ifconfig | grep 'inet addr:'| grep -v '127.0.0.1' |cut -d: -f2 | awk '{ print $1}' |
| 12 | Memory size | free -m |grep "Mem" | awk '{print $2}' |
| 13 | Check connections to port 80 | netstat -an -t | grep ":80" | grep ESTABLISHED | awk '{printf "%s %s\n",$5,$6}' | sort |
| 14 | Check concurrent connections and TCP connection status to Apache | netstat -n | awk '/^tcp/ {++S[$NF]} END {for(a in S) print a, S[a]}' |
| 15 | Check all jpg file size | find / -name *.jpg -exec wc -c {} \;|awk '{print $1}'|awk '{a+=$1}END{print a}' |
| 16 | CPU number | cat /proc/cpuinfo |grep -c processor |
| 17 | CPU load | cat /proc/loadavg |
| 18 | CPU load | mpstat 1 1 |
| 19 | Memory space | free |
| 20 | Disk usage | df -h |
| 21 | Find files and directories taking most space in a disk space | du -cks * | sort -rn | head -n 10 |
| 22 | Disk I/O load | iostat -x 1 2 |
| 23 | Network load | sar -n DEV |
| 24 | Network error | netstat -i cat /proc/net/dev |
| 25 | Network connection number | netstat -an | grep -E “^(tcp)” | cut -c 68- | sort | uniq -c | sort -n |
| 26 | Total process number | ps aux | wc -l |
| 27 | Check process tree | ps aufx |
| 28 | Number of runnable processes | vmwtat 1 5 |
| 29 | Check whether a DNS server works properly | dig www.baidu.com @61.139.2.69 |
| 30 | Check number of users logged in currently | who | wc -l |
| 31 | Check and search log | cat /var/log/rflogview/*errors grep -i error /var/log/messages grep -i fail /var/log/messages tail -f -n 2000 /var/log/messages |
| 32 | Kernel log | dmesg |
| 33 | Time | date |
| 34 | Opened handles | lsof | wc -l |
| 35 | Capture network package | tcpdump -c 10000 -i eth0 -n dst port 80 > /root/pkts |
| 36 | Check repetitions of IP and print it with lowest to largest order | less pkts | awk {'printf $3"\n"'} | cut -d. -f 1-4 | sort | uniq -c | awk {'printf $1" "$2"\n"'} | sort -n -t\ +0 |
| 37 | kudzu to check network adaptor type | kudzu --probe --class=network |
