Table of Contents

• man Command
• Flags
• Standard Output and Error

• Shell Scripting Basics

  • Variables
  • Conditionals
  • Loops
  • Functions
  • Arguments
  • Useful Shell Built-ins

---

man Command

• man displays the manual page for a command:

man ls

• Use / to search, n for next, q to quit.

---

Flags

• Flags (or options) modify the behavior of a command.

Conventions

• Single-character flags: prefixed with one dash (-a, -l, etc.)
• Multi-character flags: prefixed with two dashes (--help, --version)

Examples:

ls -l
curl --help

Not all commands follow the same syntax, but these are standard conventions in Unix-like tools.

---

Standard Output and Error

• stdout = standard output (normal output)
• stderr = standard error (for error messages)

Redirecting Output

command > file.txt     # Redirect stdout to file
command 2> error.txt   # Redirect stderr to file
command &> all.txt     # Redirect both stdout and stderr

Viewing Output

command | less         # Pipe output to pager
command | grep "word"  # Pipe output to another command

---

Shell Scripting Basics

Shell scripts are text files with shell commands, usually starting with a shebang (#!/bin/bash or #!/bin/zsh).

To create a script:

echo "#!/bin/bash" > script.sh
echo "echo Hello World" >> script.sh
chmod +x script.sh
./script.sh

---

Variables

name="Adarsh"
echo "Hello $name"

---

Conditionals

if [ $name = "Adarsh" ]; then
  echo "Welcome"
else
  echo "Access Denied"
fi

---

Loops

for i in 1 2 3; do
  echo "Number: $i"
done

while [ $count -lt 5 ]; do
  echo $count
  count=$((count + 1))
done

---

Functions

say_hello() {
  echo "Hello, $1"
}

say_hello "World"

---

Arguments

#!/bin/bash
echo "Script name: $0"
echo "First argument: $1"
echo "Total args: $#"

---

Useful Shell Built-ins

Command	Purpose
cd	Change directory
pwd	Print working dir
echo	Print to stdout
read	Get user input
exit	Exit the script

This is a solid starting point for learning shell scripting. Let me know if you want exercises or real script examples next.