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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...
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Ubuntu Java Tomcat Notes: Systemctl command to install tomcat

 1. Download tomcat and save it to /opt/tomcat

2. change permission of all files in /opt/tomcat/bin directory to +x

chmod +x /opt/tomcat/bin/

3. sudo vim /etc/systemd/system/tomcat.service

[Unit]

Description=Tomcat Web Application Container

After=network.target multi-user.target


[Service]

Type=forking

User=username #replace with your username

Group=username #replace with your groupname


Environment="CATALINA_BASE=/opt/tomcat"

Environment="CATALINA_HOME=/opt/tomcat"

Environment="CATALINA_TMPDIR=/opt/tomcat/temp"

Environment="JRE_HOME=/home/newmkg/.sdkman/candidates/java/current"

Environment="JAVA_HOME=/home/newmkg/.sdkman/candidates/java/current"

Environment="CLASSPATH=/opt/tomcat/bin/bootstrap.jar:/opt/tomcat/bin/tomcat-juli.jar"


ExecStart=/opt/tomcat/bin/startup.sh

ExecStop=/opt/tomcat/bin/shutdown.sh

Restart=on-failure


[Install]

WantedBy=multi-user.target

-------------------

4. run commands to start tomcat

sudo systemctl daemon-reload;

sudo systemctl enable tomcat.service;

sudo systemctl start tomcat.service;

5. check status of tomcat

sudo systemctl status tomcat.service;

6. in case of issue try to restart tomcat via systemctl commant

sudo systemctl restart tomcat.service;

7. Is issue not resolved, run commands

sudo systemctl stop tomcat.service;

sudo systemctl disable tomcat.service;

sudo systemctl daemon-reload.service;

8. Then delete /opt/tomcat & repeat steps 1-6 above


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If you have any doubts, please let me know.

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