Variables

2.1 Variable turlari

Nazariya

Bash da barcha o'zgaruvchilar aslida string sifatida saqlanadi, lekin kontekstga qarab raqam sifatida ishlatilishi mumkin. O'zgaruvchi nomlari faqat harflar, raqamlar va pastki chiziq (_) dan iborat bo'lishi kerak va raqam bilan boshlanmasligi kerak.

O'zgaruvchi turlari:

• Local variables - faqat joriy shell da mavjud
• Environment variables - barcha subprocess larga uzatiladi
• Shell variables - shell tomonidan maxsus ishlatiladi
• Array variables - bir nechta qiymatni saqlaydi
• Read-only variables - o'zgartirib bo'lmaydigan

Amaliyot

#!/bin/bash

# =====================================
# LOCAL VARIABLES
# =====================================

# String o'zgaruvchilar
FIRST_NAME="Ahmad"
LAST_NAME="Karimov"
FULL_NAME="$FIRST_NAME $LAST_NAME"

# Raqamli o'zgaruvchilar (aslida string)
AGE=25
YEAR=2024
SALARY=5000000

# Boolean o'zgaruvchilar (string sifatida)
IS_STUDENT=true
IS_MARRIED=false

echo "Ism: $FULL_NAME"
echo "Yosh: $AGE"
echo "Talabami: $IS_STUDENT"

# =====================================
# ENVIRONMENT VARIABLES
# =====================================

# Environment o'zgaruvchi yaratish
export DATABASE_URL="postgresql://localhost:5432/mydb"
export API_KEY="abc123xyz789"
export DEBUG_MODE="true"

# Child process da ham mavjud bo'ladi
bash -c 'echo "Child da API_KEY: $API_KEY"'

# =====================================
# ARRAY VARIABLES
# =====================================

# Oddiy array
COLORS=("qizil" "ko'k" "yashil" "sariq")
NUMBERS=(1 2 3 4 5 10 20)

# Array elementlariga kirish
echo "Birinchi rang: ${COLORS[0]}"
echo "Barcha ranglar: ${COLORS[@]}"
echo "Ranglar soni: ${#COLORS[@]}"

# =====================================
# READ-ONLY VARIABLES
# =====================================

# O'zgarmas qiymatlar
readonly PI=3.14159
readonly COMPANY_NAME="MyCompany"
readonly MAX_USERS=100

echo "PI qiymati: $PI"
# PI=3.14  # Bu xato beradi!

# =====================================
# SPECIAL VARIABLES
# =====================================

echo "Script nomi: $0"
echo "Birinchi argument: $1"
echo "Argumentlar soni: $#"
echo "Barcha argumentlar: $@"
echo "Script PID: $$"
echo "Oxirgi buyruq exit kodi: $?"

Real loyiha misoli:

#!/bin/bash
# Web application konfiguratsiyasi

# =====================================
# APPLICATION SETTINGS
# =====================================

# Read-only application constants
readonly APP_NAME="MyWebApp"
readonly APP_VERSION="2.1.0"
readonly CONFIG_DIR="/etc/myapp"

# Environment-specific variables
export ENVIRONMENT="production"  # development, staging, production
export LOG_LEVEL="INFO"          # DEBUG, INFO, WARN, ERROR

# Database configuration
export DB_HOST="localhost"
export DB_PORT="5432"
export DB_NAME="myapp_db"
export DB_USER="app_user"
# Parolni file dan o'qish (xavfsizlik uchun)
if [[ -f "/etc/myapp/db_password" ]]; then
    export DB_PASSWORD=$(cat /etc/myapp/db_password)
fi

# Server configuration
SERVER_HOST="0.0.0.0"
SERVER_PORT=8080
MAX_CONNECTIONS=1000

# Feature flags
ENABLE_CACHE=true
ENABLE_LOGGING=true
ENABLE_METRICS=false

echo "🚀 $APP_NAME v$APP_VERSION ishga tushmoqda..."
echo "📊 Environment: $ENVIRONMENT"
echo "🗄️  Database: $DB_HOST:$DB_PORT/$DB_NAME"
echo "🌐 Server: $SERVER_HOST:$SERVER_PORT"

---

2.2 Variable operations

Nazariya

O'zgaruvchilar bilan turli operatsiyalar bajarish mumkin: yaratish, o'qish, o'zgartirish, birlashtirish va qiymat tekshirish.

Asosiy operatsiyalar:

• Assignment: VAR=value
• Reading: $VAR yoki ${VAR}
• Default values: ${VAR:-default}
• String manipulation: uzunlik, kesish, almashtirish

Amaliyot

#!/bin/bash

# =====================================
# VARIABLE ASSIGNMENT
# =====================================

# To'g'ri usullar
NAME="Ahmad Karimov"           # Oddiy tayinlash
AGE=25                         # Raqam (string sifatida)
CITY="Toshkent"               # Shahar nomi

# Command output ni o'zgaruvchiga saqlash
CURRENT_DATE=$(date +%Y-%m-%d)
USER_COUNT=$(who | wc -l)
HOME_SIZE=$(du -sh $HOME | cut -f1)

echo "Bugun: $CURRENT_DATE"
echo "Foydalanuvchilar: $USER_COUNT"
echo "Home katalog hajmi: $HOME_SIZE"

# =====================================
# VARIABLE READING
# =====================================

USERNAME="john_doe"

# Oddiy o'qish
echo $USERNAME

# Xavfsiz o'qish (tavsiya etiladi)
echo "$USERNAME"

# Aniq o'qish (brace notation)
echo "${USERNAME}"

# O'zgaruvchi nomini boshqa belgilar bilan birlashtirish
echo "${USERNAME}_backup"      # john_doe_backup
echo "$USERNAMEbackup"         # bo'sh (noto'g'ri)

# =====================================
# DEFAULT VALUES
# =====================================

# Agar o'zgaruvchi bo'sh yoki mavjud bo'lmasa, default qiymat ishlatish
DATABASE_HOST=${DATABASE_HOST:-"localhost"}
SERVER_PORT=${SERVER_PORT:-8080}
LOG_LEVEL=${LOG_LEVEL:-"INFO"}

echo "Database server: $DATABASE_HOST"
echo "Server port: $SERVER_PORT"
echo "Log level: $LOG_LEVEL"

# Alternative value - agar o'zgaruvchi mavjud bo'lsa, boshqa qiymat ishlatish
DEBUG_MODE="true"
LOG_FILE=${DEBUG_MODE:+"debug.log"}
echo "Log file: ${LOG_FILE:-"production.log"}"

# Error agar o'zgaruvchi bo'sh bo'lsa
REQUIRED_API_KEY=${API_KEY:?"API_KEY environment variable kerak!"}

# =====================================
# STRING MANIPULATION
# =====================================

TEXT="Hello World from Uzbekistan"

# String uzunligi
echo "Matn uzunligi: ${#TEXT}"

# Substring (kesish)
echo "Birinchi 5 belgi: ${TEXT:0:5}"        # Hello
echo "6-belgidan boshlab: ${TEXT:6}"        # World from Uzbekistan  
echo "Oxirgi 10 belgi: ${TEXT: -10}"       # Uzbekistan

# Case conversion (Bash 4.0+)
UPPER_TEXT="${TEXT^^}"                      # HELLO WORLD FROM UZBEKISTAN
LOWER_TEXT="${TEXT,,}"                      # hello world from uzbekistan
TITLE_TEXT="${TEXT^}"                       # Hello world from uzbekistan

echo "Katta harf: $UPPER_TEXT"
echo "Kichik harf: $LOWER_TEXT"
echo "Title case: $TITLE_TEXT"

# =====================================
# PATTERN REPLACEMENT
# =====================================

FILENAME="document.txt.backup"

# Birinchi match ni almashtirish
NEW_NAME="${FILENAME/txt/pdf}"              # document.pdf.backup

# Barcha match larni almashtirish  
ALL_REPLACED="${FILENAME//./}"              # documenttxtbackup

# Prefix/suffix o'chirish
NO_EXTENSION="${FILENAME%.*}"               # document.txt
JUST_NAME="${FILENAME%%.*}"                 # document
NO_PATH="${FILENAME##*/}"                   # document.txt.backup

echo "Asl fayl: $FILENAME"
echo "Extension o'zgartirilgan: $NEW_NAME"
echo "Nuqtalar o'chirilgan: $ALL_REPLACED"
echo "Extension o'chirilgan: $NO_EXTENSION"
echo "Faqat nom: $JUST_NAME"

Real-world variable management misoli:

#!/bin/bash
# Configuration manager script

# =====================================
# CONFIGURATION VARIABLES
# =====================================

# Default konfiguratsiya
CONFIG_FILE="${CONFIG_FILE:-/etc/myapp/config.conf}"
LOG_DIR="${LOG_DIR:-/var/log/myapp}"
DATA_DIR="${DATA_DIR:-/var/lib/myapp}"
TMP_DIR="${TMP_DIR:-/tmp/myapp}"

# =====================================
# VALIDATION FUNCTIONS
# =====================================

validate_config() {
    local errors=0
    
    # Required variables tekshirish
    if [[ -z "${DATABASE_URL:-}" ]]; then
        echo "❌ ERROR: DATABASE_URL majburiy o'zgaruvchi"
        ((errors++))
    fi
    
    if [[ -z "${API_SECRET:-}" ]]; then
        echo "❌ ERROR: API_SECRET majburiy o'zgaruvchi"
        ((errors++))
    fi
    
    # Kataloglar mavjudligini tekshirish
    for dir in "$LOG_DIR" "$DATA_DIR" "$TMP_DIR"; do
        if [[ ! -d "$dir" ]]; then
            echo "⚠️  WARNING: Katalog mavjud emas: $dir"
            mkdir -p "$dir" && echo "✅ Katalog yaratildi: $dir"
        fi
    done
    
    return $errors
}

# =====================================
# ENVIRONMENT SETUP
# =====================================

setup_environment() {
    echo "🔧 Environment sozlanmoqda..."
    
    # Default qiymatlar o'rnatish
    export NODE_ENV="${NODE_ENV:-production}"
    export PORT="${PORT:-3000}"
    export WORKERS="${WORKERS:-$(nproc)}"
    
    # Feature flags
    export ENABLE_METRICS="${ENABLE_METRICS:-true}"
    export ENABLE_CACHE="${ENABLE_CACHE:-true}"
    export ENABLE_DEBUG="${ENABLE_DEBUG:-false}"
    
    # Security settings
    export SESSION_SECRET="${SESSION_SECRET:-$(openssl rand -hex 32)}"
    export JWT_EXPIRES_IN="${JWT_EXPIRES_IN:-1d}"
    
    echo "✅ Environment tayyor"
}

# =====================================
# CONFIGURATION DISPLAY
# =====================================

show_config() {
    echo "📋 Joriy konfiguratsiya:"
    echo "   CONFIG_FILE: $CONFIG_FILE"
    echo "   LOG_DIR: $LOG_DIR"
    echo "   DATA_DIR: $DATA_DIR"
    echo "   NODE_ENV: ${NODE_ENV:-unset}"
    echo "   PORT: ${PORT:-unset}"
    echo "   WORKERS: ${WORKERS:-unset}"
    echo
    
    echo "🔒 Security:"
    echo "   SESSION_SECRET: ${SESSION_SECRET:0:8}... (hidden)"
    echo "   JWT_EXPIRES_IN: ${JWT_EXPIRES_IN:-unset}"
    echo
    
    echo "🚀 Features:"
    echo "   METRICS: ${ENABLE_METRICS:-false}"
    echo "   CACHE: ${ENABLE_CACHE:-false}"
    echo "   DEBUG: ${ENABLE_DEBUG:-false}"
}

# =====================================
# MAIN SCRIPT
# =====================================

main() {
    echo "🔧 Application konfiguratsiya boshqaruvchisi"
    echo "================================================"
    
    setup_environment
    
    if validate_config; then
        echo "✅ Konfiguratsiya to'g'ri"
        show_config
    else
        echo "❌ Konfiguratsiya xatolari topildi"
        exit 1
    fi
}

# Script ishga tushirish
main "$@"

Variable debugging va troubleshooting:

#!/bin/bash

# =====================================
# DEBUGGING VARIABLES
# =====================================

debug_variables() {
    echo "🐛 Variable debugging"
    echo "===================="
    
    # Barcha o'zgaruvchilarni ko'rsatish
    echo "📊 Environment variables:"
    env | grep -E "^(PATH|HOME|USER|SHELL)" | sort
    echo
    
    # Local variables
    echo "📝 Local variables:"
    set | grep -E "^[A-Z_].*=" | head -10
    echo
    
    # Specific variable haqida ma'lumot
    local var_name="PATH"
    echo "🔍 $var_name haqida:"
    echo "   Qiymat: ${!var_name}"
    echo "   Uzunlik: ${#PATH}"
    echo "   Type: $(declare -p PATH 2>/dev/null | cut -d' ' -f2)"
}

# Variable export status tekshirish
check_export_status() {
    local var_name="$1"
    
    if declare -p "$var_name" 2>/dev/null | grep -q "declare -x"; then
        echo "✅ $var_name exported (global)"
    else
        echo "📍 $var_name local variable"
    fi
}

# Variable type aniqlash
get_variable_type() {
    local var_name="$1"
    local declaration
    
    declaration=$(declare -p "$var_name" 2>/dev/null)
    
    case "$declaration" in
        *"declare -a"*) echo "Array" ;;
        *"declare -A"*) echo "Associative Array" ;;
        *"declare -i"*) echo "Integer" ;;
        *"declare -r"*) echo "Read-only" ;;
        *"declare -x"*) echo "Exported" ;;
        *"declare --"*) echo "String" ;;
        *) echo "Unknown/Unset" ;;
    esac
}

# Test
debug_variables
check_export_status "PATH"
check_export_status "HOME"
echo "PATH type: $(get_variable_type "PATH")"

Bu 2-bob bo'yicha to'liq qo'llanma. 3-bob (Input/Output) uchun ham yozamanmi?