Merge pull request #1 from zakaria1193/split-tips

Split tips into separate clean markdown files

i3/tips.md → tips/i3_tips.md

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 xmodmap -pke
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tips/shell_tips.md

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+# Shell Tips
+
+## Basic Commands
+
+- `which` - shows where the binary for a command is located
+- `whereis` - similar to `which` but also looks in packages
+- `type` - shows if a command is an alias, builtin, etc.
+- `eval` - evaluates a string as a command
+- `exec` - replaces the current shell with the specified command
+- `command` - runs the specified command, ignoring shell functions and aliases
+- `file` - shows the type of a file (e.g., `file /usr/bin/python3.4` says it's an ELF 64-bit executable)
+- `ls -i` - shows inode numbers
+- `shutdown now` - shuts down the system immediately (`-r` to reboot, can specify a delay)
+- `tee` - takes the output from a command and saves it to a file while also sending it to standard output (e.g., `ls -l | tee newfile`)
+- `tac` - concatenates and prints files in reverse
+- `tail` and `head` - show the last or first lines of a file (`tail -n 15 file` for the last 15 lines, `tail -f file` to follow new lines added to a file)
+- `touch -t 03201600 myfile` - sets the date of a file
+- `rm -i` - interactive removal, useful when using patterns
+- `PS1` - sets the terminal prompt
+- `man` and `info` - provide information on commands
+- `help` - provides information on built-in shell commands
+
+## Advanced Commands
+
+### AWK, SED, GREP, FIND
+
+- `AWK` - for advanced data extraction
+  - `awk '{ print $0 }' /etc/passwd` - print entire file
+  - `awk -F: '{ print $1 }' /etc/passwd` - print first field of every line
+  - `awk -F: '{ print $1 $7 }' /etc/passwd` - print first and seventh fields of every line
+
+- `SED` - for simple text manipulation, mostly search and replace
+  - `sed s/pattern/replace_string/ file` - substitute first occurrence of pattern in a line
+  - `sed s/pattern/replace_string/g file` - substitute all occurrences of pattern in a line
+  - `sed 1,3s/pattern/replace_string/g file` - substitute all occurrences of pattern between lines 1 and 3
+  - `sed -i s/pattern/replace_string/g file` - save changes for string substitution in the same file
+
+- `GREP` - for searching text using patterns
+  - `grep [pattern] <filename>` - search for a pattern in a file and print all matching lines
+  - `grep [0-9] <filename>` - print lines that contain numbers 0 through 9
+  - `grep -r [pattern] [path]` - recursive search in directories
+  - `grep -v [pattern] [path]` - print lines that do NOT match the pattern
+  - `grep -C n [pattern] [path]` - print lines with a context of n lines
+
+- `FIND` - for searching files and directories
+  - `find [where] -name [pattern]` - search for files matching the pattern
+  - `find [where] -iname [pattern]` - case-insensitive search
+  - `find [where] -name "*.swp" -exec rm {} \;` - delete all files matching the pattern
+  - `find / -ctime 3` - find all files changed 3 minutes ago
+  - `find / -size +10M -exec rm {} \;` - delete files larger than 10M
+
+- `LOCATE` - for finding files using a database
+  - `locate [pattern]` - search for files matching the pattern
+  - `locate -b [pattern]` - search using globbing pattern
+  - `locate --regex [pattern]` - search using regex
+
+### File Types
+
+- `-` : regular file
+- `d` : directory
+- `c` : character device file
+- `b` : block device file
+- `s` : local socket file
+- `p` : named pipe
+- `l` : symbolic link
+
+## Programming
+
+### Opening Binary Files
+
+- `hexdump -C x.bin` - shows the strings in the binary
+- `strings x.bin` - shows the strings only, can show library calls
+- `objdump -d x.bin` - disassembles the whole binary
+- `objdump -x x.bin` - shows the sections and other interesting info
+- `nm x.bin` - dumps the symbols
+- `readelf -a x.bin` - like objdump but better for ELF files
+- `strace x.bin` - shows all syscalls made by the program
+- `ltrace x.bin` - shows all dynamic library calls
+- `gdb x.bin` - GNU Debugger
+- `r2 x.bin` - radare2 (type `aaa` at first to analyze the program, a lot of cool stuff like `VV` for visual disassembly mode)
+
+## Processes
+
+### Managing Processes
+
+- `ps` - shows processes associated with the invoking terminal
+- `ps -elf` - shows all threads (not only processes)
+- `pstree` - shows the process tree
+- `w` or `top` or `htop` - shows load on CPU of each process
+- `kill -SIGKILL <pid>` - forcefully kill a process
+- `kill -9 <pid>` - forcefully kill a process
+- `CTRL-Z` - suspend a process (in foreground)
+- `jobs` - shows processes in the background of a terminal
+
+### Process Types
+
+- Interactive Processes - need to be started by a user (e.g., `bash`, `firefox`, `top`)
+- Batch Processes - automatic processes scheduled and disconnected from the terminal (e.g., `updatedb`)
+- Daemons - server processes that run continuously (e.g., `httpd`, `xinetd`, `sshd`)
+- Threads - lightweight processes that share memory and resources (e.g., `firefox`, `gnome-terminal-server`)
+- Kernel Threads - kernel tasks that users have little control over (e.g., `kthreadd`, `migration`, `ksoftirqd`)
+
+### Fork and Exec
+
+- `fork` - creates a new process (child process) with the same environment as the parent process
+- `exec` - replaces the contents of the currently running process with the information from a program binary
+
+## Web Networking
+
+### HTTP
+
+- `wget` - downloads a webpage (e.g., `wget http://example.com`)
+
+### TCP
+
+- `netcat` - TCP tool
+  - `echo 'HEAD / HTTP/1.1\r\nHost: www.google.com\r\n\r\n' | nc www.google.com 80` - send HTTP request with netcat
+  - `nc -l 3333` - plain TCP server listening on port 3333
+  - `nc localhost 3333` - connect to the TCP server on port 3333
+
+- `tcpdump` - network packet analyzer
+  - `tcpdump -n host 8.8.8.8` - show ICMP ping packets
+  - `tcpdump -n port 53` - show DNS packets
+  - `tcpdump -n port 80` - show HTTP packets
+
+### DNS
+
+- `nslookup` or `host` or `dig` - perform a DNS lookup
+- `dig` - provides more details on how the DNS query was resolved
+
+### IP/Subnetting
+
+- `ip addr show` or `ifconfig` - show network interfaces
+- `traceroute hostname` or `traceroute ip_address` or `mtr hostname` - show the routes traffic might take
+- `ping` - gives round trip time (RTT)
+- `ethtool <interface>` - shows the capabilities of the network hardware
+- `arp` - shows MAC addresses of recent devices in the network
+- `netstat -s` - network status information and statistics
+- `netstat -t -n` - shows current TCP connections
+- `netstat -t -n -l` - shows only listening TCP connections
+
+### Firewall
+
+- Common configuration: drop any incoming traffic except traffic to (host, port) pairs that are supposed to be receiving connections from the Internet
+