备考入门方法咨询与listfiles Shell脚本开发需求问询

Hey there! Let's tackle your two requests one at a time—first the study prep guidance, then building that listfiles shell script.

Don’t stress, it’s totally normal to feel stuck when starting exam prep! Here are some down-to-earth steps to get you going:

• Build a framework first, then fill in details: Start by mapping out the core knowledge structure of your exam subject (e.g., for Linux admin, split into file systems, command line, scripting, service management). Don’t get bogged down in tiny details right away—focus on understanding the big picture first.
• Start with official basic docs: Skip flashy "crash courses" and dive into official beginner tutorials or manuals (like the man pages for basic Linux commands). A solid foundation prevents bad habits later on.
• Learn with small, task-driven practice: Don’t just read—pick simple, concrete tasks (e.g., "count files in a directory with commands," "write a basic backup script") and learn by doing. It’s way more effective than rote memorization.
• Stick to a consistent rhythm: Dedicate 1-2 hours daily to focused study, no need to cram. For example, learn one module each day, then review the week’s content on weekends and tackle any confusing points.
• Connect with peers: Chat with others who’re also prepping. Sometimes a quick question to a fellow learner can clear up a stuck point faster than hours of googling.

I’ll walk you through building this script step by step, with explanations so you understand every part:

需求回顾 #

Here’s a quick recap of what the script needs to do:

Accept two command-line arguments: the first is a directory name, the second is a file size in bytes. Call it like $ listfiles /tmp 50. First check if exactly 2 arguments are passed, then verify the first argument is a valid directory, finally list all regular files in that directory with read permissions.

分步实现 #

Step 1: Check the number of arguments #

First, we need to make sure the user passed exactly 2 arguments. If not, show a usage prompt and exit:

if [ $# -ne 2 ]; then
    echo "Usage error: Please pass 2 arguments, format:"
    echo "  listfiles <target-directory> <min-file-size-in-bytes>"
    exit 1
fi

Step 2: Validate the directory #

Next, check if the first argument is actually a directory. If not, throw an error and exit:

TARGET_DIR="$1"
MIN_SIZE="$2"

if [ ! -d "$TARGET_DIR" ]; then
    echo "Error: '$TARGET_DIR' is not a valid directory"
    exit 1
fi

Step 3: Find qualifying files #

We’ll use the find command to filter files that meet all requirements:

• -type f: Only target regular files (not directories, symlinks, etc.)
• -readable: Ensure the current user has read permission
• -size +${MIN_SIZE}c: The c denotes bytes, and + means "larger than" (use - for smaller than, or no symbol for exact size)
• -maxdepth 1: Only look in the target directory itself (not subdirectories—remove this if you want recursive search)

Here’s the code for this part:

echo "=== Results: Qualifying files in $TARGET_DIR ==="
find "$TARGET_DIR" -maxdepth 1 -type f -readable -size +${MIN_SIZE}c

完整脚本 #

Putting it all together, here’s the full listfiles script:

#!/bin/bash

# Check number of arguments
if [ $# -ne 2 ]; then
    echo "Usage error: Please pass 2 arguments, format:"
    echo "  listfiles <target-directory> <min-file-size-in-bytes>"
    exit 1
fi

TARGET_DIR="$1"
MIN_SIZE="$2"

# Validate directory exists
if [ ! -d "$TARGET_DIR" ]; then
    echo "Error: '$TARGET_DIR' is not a valid directory"
    exit 1
fi

# Find and print qualifying files
echo "=== Results: Qualifying files in $TARGET_DIR ==="
find "$TARGET_DIR" -maxdepth 1 -type f -readable -size +${MIN_SIZE}c

使用说明 #

1. Save the script as listfiles
2. Give it execute permissions: chmod +x listfiles
3. Run it like this: ./listfiles /tmp 50
   • This will list all regular files in /tmp that are over 50 bytes and readable by you.

内容的提问来源于stack exchange，提问作者thisguy