Bash Arrays, Strings, and Text Handling

files=(a.txt b.txt c.txt)

# Create an indexed array.

echo "${files[1]}"

# Read an array element by index.

printf '%s
' "${files[@]}"

# Expand all array items safely.

echo "${#files[@]}"

# Count array elements.

files+=(d.txt)

# Append one or more elements to an array.

for f in "${files[@]}"; do echo "$f"; done

# Iterate through array elements safely.

unset 'files[1]'

# Remove one indexed element.

declare -A ports=([http]=80 [https]=443)

# Declare an associative array.

echo "${ports[https]}"

# Read a value by key.

printf '%s
' "${!ports[@]}"

# Expand associative array keys.

for k in "${!ports[@]}"; do echo "$k=${ports[$k]}"; done

# Iterate through an associative array.

name='Hello World'
echo "${name,,}"

# Convert a string to lowercase.

name='Hello World'
echo "${name^^}"

# Convert a string to uppercase.

url='https://example.com'
echo "${url#https://}"

# Strip a matching prefix from a string.

file='archive.tar.gz'
echo "${file%.gz}"

# Strip a matching suffix from a string.

IFS=, read -r -a parts <<< 'red,green,blue'
printf '%s
' "${parts[@]}"

# Split a delimited string into an array.

(IFS=,; echo "${parts[*]}")

# Join array elements using IFS.

read -r -p 'Enter name: ' name

# Read one line from stdin with a prompt.

read -r -s -p 'Password: ' password; echo

# Read secret input without echoing characters.

mapfile -t lines < file.txt

# Read all lines of a file into an array.

IFS=: read -r user shell <<< 'root:/bin/bash'
echo "$user $shell"

# Parse delimited input into multiple variables.