Skip to main content

How to use gdb in Ubuntu Terminal

Here's a practical, minimal guide for using GDB in Ubuntu terminal — from launching to setting breakpoints and navigating your code. 🧰 Step 1: Compile with Debug Symbols Use -g and disable optimizations ( -O0 preferred for debugging): bash Copy Edit g++ -g -O0 -o myprog myprog.cpp 🚀 Step 2: Launch GDB bash Copy Edit gdb ./myprog You'll see a (gdb) prompt. 🎯 Step 3: Set Breakpoints You can set breakpoints in three main ways : ✅ a. At a function gdb Copy Edit (gdb) break main ✅ b. At a specific file and line gdb Copy Edit (gdb) break myprog.cpp:42 ✅ c. At a method in a class gdb Copy Edit (gdb) break MyClass::doSomething If the symbol is mangled (C++), GDB usually demangles automatically, especially if compiled with -g . ▶️ Step 4: Run the Program gdb Copy Edit (gdb) run 🧭 Step 5: Navigate Command Meaning next or n Step over current line step or s Step into function call finish Run until current function returns continue or c Continue until...

Notes: Java module to convert list of images to PDF document using Apache PDFBox

 private static void convertImagesToPdf(ArrayList<String> imagesFilePath, String pdfFilePath) throws Exception {

        try ( PDDocument doc = new PDDocument();) {

            for (String imageFilePath : imagesFilePath) {

                PDImageXObject image = PDImageXObject.createFromFile(imageFilePath, doc);

                PDRectangle pageSize = PDRectangle.A4;

                int originalWidth = image.getWidth();

                int originalHeight = image.getHeight();

                float pageWidth = pageSize.getWidth();

                float pageHeight = pageSize.getHeight();

                float ratio = Math.min(pageWidth / originalWidth, pageHeight / originalHeight);

                float scaledWidth = originalWidth * ratio;

                float scaledHeight = originalHeight * ratio;

                float x = (pageWidth - scaledWidth) / 2;

                float y = (pageHeight - scaledHeight) / 2;

                PDPage page = new PDPage(pageSize);

                doc.addPage(page);

                try ( PDPageContentStream contents = new PDPageContentStream(doc, page)) {

                    contents.drawImage(image, x, y, scaledWidth, scaledHeight);

                }

            }

            doc.save(pdfFilePath);

        }

    }

Comments

Popular posts from this blog

Ubuntu Notes: Set up autossh as systemd useful-reminder commands

 sudo vim /etc/systemd/system/permanentAutossh.service ======================================== [Unit] Description=Keeps a tunnel to myOciFreeNat open After=network-online.target [Service] User=<username> Environment="AUTOSSH_GATETIME=0" ExecStart=/usr/bin/autossh -M 0 -q -N -o "ServerAliveInterval 60" -o "ServerAliveCountMax 3" -L 4322:127.0.0.1:5432 -i /<ssh_private_key_file_absolute_path> <username>@<ip_address> -p 22 [Install] WantedBy=multi-user.target ======================================== sudo systemctl daemon-reload sudo systemctl enable permanentAutossh sudo systemctl start permanentAutossh ================== sudo systemctl daemon-reload sudo systemctl restart permanentAutossh sudo systemctl status permanentAutossh ====================== sudo systemctl stop permanentAutossh sudo systemctl disable permanentAutossh sudo rm /etc/systemd/system/permanentAutossh.service

syslog cpp programming: learning using chatGcp

  Introduction to Syslog C++ August 27, 2024 This conversation may reflect the link creator’s personalized data, which isn’t shared and can meaningfully change how the model responds. You said: I am new to syslog in cpp programming n just starting. Can you teach me ChatGPT said: ChatGPT Sure! syslog is a standard for logging system messages in Unix-like operating systems. It provides a way to send log messages to the system log, which can then be collected and analyzed by various tools. Here's a basic guide to get you started with syslog in C++: 1. Include the Necessary Header To use syslog , you need to include the syslog.h header: cpp Copy code # include <syslog.h> 2. Open the Connection to syslog Before sending log messages, you need to open a connection to the syslog system. This is typically done at the start of your program: cpp Copy code openlog ( "your_program_name" , LOG_PID | LOG_CONS, LOG_USER); "your_program_name" : A string representing ...

Ubuntu - C++ Notes: Install & update boost c++ library from git (may contain some error in process mentioned below)

 Boost C++ Library Installation from git in ubuntu: 1. create a directory named boost in your desired location and go to that directory mkdir boost;cd boost; 2. clone boost recursively from git using command git clone --recursive https://github.com/boostorg/boost.git 3. cd boost; sudo ./bootstrap.sh; 4. sudo ./b2; 5. sudo ./b2 install; DONE! --------------------------- Boost C++ Library Update Verson from git in Ubuntu: 1. go to gitDownloads/boost directory cd gitDownloads/boost; 2. git pull; 3. git submodule update --recursive; 4. cd boost; sudo ./bootstrap.sh; 5. sudo ./b2; 6. sudo ./b2 install; DONE!