Boost Your Linux Productivity: 9 Essential Commands You Might Be Missing

strace

strace tracks system calls made by a program. Basic usage to trace a process: strace -p [test_pid] Or run the program directly: strace ./test Useful options: -f – follow child processes (threads). -C – count occurrences of each system call. -e trace=network – show only network‑related calls. -e trace=open,close,read,write – filter specific calls. -ttt – display timestamps. -s 1024 – increase the maximum string length displayed.

Example: trace all read and write calls of every thread in process 12345, with strings up to 1024 bytes:

strace -s 1024 -f -e trace=read,write -p 12345

tcpdump

tcpdump captures network packets. Capture all traffic on interface eth0: sudo tcpdump -i eth0 Common options: -A – print packets in ASCII. -X – print packets in both hex and ASCII. -w file – write raw packets to file (e.g., -w 1.cap). host 11.11.11.11 and port 12345 – filter by host and port.

Example: capture HTTP traffic on port 80 and display it as text:

sudo tcpdump -i any port 80 -A

nc (netcat)

nc can create TCP/UDP clients and servers.

TCP server on port 12345: nc -l 127.0.0.1 12345 TCP client connecting to the same address: nc 127.0.0.1 12345 UDP server: nc -ul 127.0.0.1 12345 UDP client: nc -u 127.0.0.1 12345 Unix‑domain socket server: nc -Ul /tmp/1.sock Unix‑domain socket client:

nc -U /tmp/1.sock

curl

curl performs HTTP requests from the terminal.

Simple GET request: curl http://www.baidu.com Important options: -H "Host: xx.xx.xx.xx" – set a custom Host header. -X POST – specify request method; -d "data" adds POST data. -v – verbose output, showing request and response headers. -L – follow redirects. -sSfL – silent, show errors, fail on HTTP errors, follow redirects.

find

find searches for files. Find a file named 1.txt in the current directory tree: find . -name "1.txt" Combine with xargs to search file contents: find . -type f | xargs grep 'abcd' This lists all files containing the string abcd .

lsof

lsof lists open files and sockets. sudo lsof -i :[port] – show which process is using a given port. sudo lsof -p [pid] – list files opened by a specific process. ss ss replaces netstat and is faster because it reads /proc/net directly. ss -t -a – show all TCP sockets. ss -u -a – show all UDP sockets. ss -x src /tmp/a.sock – show processes using a Unix socket. ss -o state established – list all established connections. awk / sed awk processes text by columns; sed processes by lines. Print the first field of a colon‑separated file: <code>awk -F ":" '{print $1}' file</code> Show lines 100‑200 of a file: <code>sed -n '100,200p' log.txt</code> Replace a substring in a file: <code>sed "s/charset=gb2312/charset=UTF-8/g" test</code> screen screen creates detachable terminal sessions, useful when SSH connections drop. screen -S test – start a new session named test . Ctrl‑a d – detach from the session. screen -ls – list existing sessions. screen -r 13333.test – reattach to a specific session. exit – close the current screen session. Note: This article assumes familiarity with common commands such as top , netstat , df , and vmstat . The examples focus on less‑known but practical options; consult each command’s manual for the full feature set.