When porting Linux shell scripts to macOS, one of the most frustrating differences is how zcat behaves differently between the platforms. Here's the technical breakdown:

# On Linux:
zcat file.zip → works with ZIP archives

# On macOS:
zcat file.zip → looks for file.zip.Z (fails)
gzcat file.zip → expects gzip format (fails)

The divergence comes from Unix history - macOS inherits the BSD behavior where:

• zcat traditionally handled .Z (compress) files
• Linux systems typically symlink zcat to gzip's functionality

For cross-platform ZIP file handling in scripts, consider these approaches:

# Option 1: Use unzip -c
unzip -c archive.zip file_inside.txt

# Option 2: Detect platform and switch behavior
if [[ "$OSTYPE" == "linux-gnu"* ]]; then
    zcat file.zip
elif [[ "$OSTYPE" == "darwin"* ]]; then
    unzip -p file.zip
fi

For more robust scripting:

# Create wrapper functions in your .bashrc/.zshrc
zcat() {
    case "$(uname -s)" in
        Linux*) command zcat "$@";;
        Darwin*) 
            if file "$1" | grep -q 'Zip archive'; then
                unzip -p "$@"
            else
                command gzcat "$@"
            fi;;
    esac
}

• pigz: Multi-threaded gzip compatible with both platforms
• p7zip: Unified archive handling (brew install p7zip on macOS)
• bsdtar: Available on both platforms with consistent behavior

Here's how to verify your solution works:

#!/bin/bash

# Create test files
echo "test" > test.txt
zip test.zip test.txt
gzip test.txt

# Test function
test_zcat() {
    echo -n "Testing $1: "
    if zcat "$1" 2>/dev/null | grep -q test; then
        echo "PASSED"
    else
        echo "FAILED"
    fi
}

test_zcat test.zip
test_zcat test.txt.gz

During my recent cross-platform scripting work, I encountered a frustrating discrepancy between Linux and macOS when using zcat with ZIP files. Here's the exact behavior:

# Linux (works):
zcat archive.zip | head

# macOS (fails):
zcat: can't stat: archive.zip.Z (.Z extension automatically appended)
gzcat archive.zip
gzip: archive.zip: not in gzip format

The root cause stems from historical differences in Unix implementations:

• Linux zcat: Part of gzip utilities, handles .gz files by default
• macOS zcat: From BSD heritage, expects older .Z compress format
• macOS gzcat: Equivalent to Linux's zcat but still fails with ZIPs

The file command confirms our file is actually a ZIP archive, not gzip-compressed:

file archive.zip
archive.zip: Zip archive data, at least v2.0 to extract

Here are three reliable approaches I've tested:

1. Using unzip with stdout

# Works on both platforms
unzip -p archive.zip | head

The -p flag extracts files to pipe (stdout), similar to zcat's behavior.

2. Platform-aware wrapper function

zcat_zip() {
  case "$(uname)" in
    Linux*) zcat "$@" ;;
    Darwin*) unzip -p "$@" ;;
  esac
}

# Usage:
zcat_zip archive.zip | awk '{print $1}'

3. Install GNU coreutils via Homebrew

For macOS users who prefer Linux-style tools:

brew install coreutils
gzcat archive.zip | sed 's/foo/bar/'

For complex workflows, consider these additional strategies:

• Implement feature detection instead of OS detection
• Standardize on ZIP or gzip format across environments
• Use containerization (Docker) for identical environments

# Example feature detection
if command -v unzip &>/dev/null; then
  ZIP_READER="unzip -p"
elif command -v zcat &>/dev/null; then
  ZIP_READER="zcat"
fi

$ZIP_READER data.zip | process_data

Remember that ZIP and gzip are different formats - ZIP is an archive format that can contain multiple compressed files, while gzip compresses a single stream.