Having used zsh for years after transitioning from tcsh/csh, I've often wondered about the unique capabilities each shell offers. While both are powerful, they have distinct technical advantages worth examining.

# 1. Process substitution with <() and >()
diff <(sort file1) <(sort file2)

# 2. Special array variables
echo "${!BASH_*}"  # Expands to all bash-specific variables

# 1. Globbing qualifiers
ls *(.mm-1)  # Modified in last minute
print -l /usr/bin/*(u[$(id -u)])

# 2. Advanced pattern matching
setopt EXTENDED_GLOB
echo ^*.txt  # All files except .txt

• Array indexing: Bash starts at 0, zsh at 1
• Word splitting: Zsh doesn't do it by default
• Globbing: Zsh has recursive (**/) and qualifiers

For system scripting where portability matters, Bash's universal availability makes it ideal:

#!/bin/bash
# Works on nearly any Linux/Unix system
for i in {1..10}; do
  echo "Processing item $i"
done

Interactive use benefits from zsh's rich completion system:

# Set completion options
zstyle ':completion:*' menu select
zstyle ':completion:*' matcher-list 'm:{a-z}={A-Z}'

# Powerful directory navigation
cd /u/l/b  # Expands to /usr/local/bin

As shells evolved over decades, bash (Bourne-Again SHell) and zsh (Z Shell) developed distinct capabilities. Here's a technical breakdown of features unique to each:

# Process substitution with <() syntax (not in zsh)
diff <(sort file1) <(sort file2)

# POSIX-compliant arithmetic expansion
result=$(( 10#$(date +%H) * 60 + 10#$(date +%M) ))

# Special parameter expansions
${parameter/pattern/string}  # Pattern substitution
${parameter:offset:length}   # Substring expansion

# Extended globbing
print -l **/*.txt(N)  # Nullglob pattern
print -l *(^x)        # Negation operator

# Advanced array operations
array=(one two three)
print ${(j:,:)array}  # Join elements with comma

# Floating-point arithmetic
% print $(( 1.5 * 3 ))
4.5000000000

zsh strengths:

• Context-aware tab completion (type 'git ' then press tab)
• Themes and plugins via frameworks like Oh-My-Zsh
• Spelling correction (setopt CORRECT)

bash strengths:

• More predictable behavior across different Unix systems
• Simpler configuration syntax for basic needs
• Better compatibility with legacy shell scripts

Benchmark tests show:

For bash users switching to zsh:

# Enable bash compatibility mode
emulate -LR bash
setopt SH_WORD_SPLIT
setopt KSH_ARRAYS

For zsh users switching to bash:

# Simulate some zsh features
shopt -s extglob       # Extended pattern matching
shopt -s globstar      # ** recursive matching
complete -D -F _longopt # Better completion