# Unable to Launch ROS Package Exercise 3.1

**URL:** <https://get-help.theconstruct.ai/t/unable-to-launch-ros-package-exercise-3-1/26799>\
**Category:** ROS Basics In 5 Days (Python)\
**Created:** [October 12, 2023, 1:45pm UTC](https://get-help.theconstruct.ai/t/unable-to-launch-ros-package-exercise-3-1/26799 "2023-10-12T13:45:05Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![asghar.arafat](https://get-help.theconstruct.ai/letter_avatar_proxy/v4/letter/a/3ab097/32.png) [@asghar.arafat](https://get-help.theconstruct.ai/u/asghar.arafat)\
**Post date:** [October 12, 2023, 1:45pm UTC](https://get-help.theconstruct.ai/t/unable-to-launch-ros-package-exercise-3-1/26799/1 "2023-10-12T13:45:05Z")

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I am getting the following error:

RLException: Invalid roslaunch XML syntax: mismatched tag: line 3, column 2  
The traceback for the exception was written to the log file

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**Author:** ![albertoezquerro](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/albertoezquerro/32/7031_2.png) [@albertoezquerro](https://get-help.theconstruct.ai/u/albertoezquerro)\
**Post date:** [October 13, 2023, 7:17am UTC](https://get-help.theconstruct.ai/t/unable-to-launch-ros-package-exercise-3-1/26799/2 "2023-10-13T07:17:36Z")

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Hello @asghar.arafat ,

This looks like you have a syntax error in your launch file. Can you copy the file contents here?

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**Author:** ![asghar.arafat](https://get-help.theconstruct.ai/letter_avatar_proxy/v4/letter/a/3ab097/32.png) [@asghar.arafat](https://get-help.theconstruct.ai/u/asghar.arafat)\
**Post date:** [October 13, 2023, 2:14pm UTC](https://get-help.theconstruct.ai/t/unable-to-launch-ros-package-exercise-3-1/26799/3 "2023-10-13T14:14:20Z")

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Dear @albertoezquerro. Thank you for your response.

My launch file is given as under:

The python file simple\_topic\_publisher.py is given as follows:

#! /usr/bin/env python

import rospy

from geometry\_msgs.msg import Twist

rospy.init\_node(‘move\_robot\_node’)

pub = rospy.Publisher(‘/cmd\_vel’, Twist, queue\_size=1)

rate = rospy.Rate(2)

move = Twist()

move.linear.x = 0.5

move.linear.z = 0.5

while not rospy.is\_shutdown():

pub.publish(move)

rate.sleep()

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<div class="post-metadata">

**Author:** ![albertoezquerro](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/albertoezquerro/32/7031_2.png) [@albertoezquerro](https://get-help.theconstruct.ai/u/albertoezquerro)\
**Post date:** [October 16, 2023, 7:49am UTC](https://get-help.theconstruct.ai/t/unable-to-launch-ros-package-exercise-3-1/26799/4 "2023-10-16T07:49:57Z")

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Hello @asghar.arafat ,

I don’t see any launch file in your response, only the Python code.

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**Author:** ![asghar.arafat](https://get-help.theconstruct.ai/letter_avatar_proxy/v4/letter/a/3ab097/32.png) [@asghar.arafat](https://get-help.theconstruct.ai/u/asghar.arafat)\
**Post date:** [October 17, 2023, 6:47am UTC](https://get-help.theconstruct.ai/t/unable-to-launch-ros-package-exercise-3-1/26799/5 "2023-10-17T06:47:05Z")

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Dear @albertoezquerro,

My apologies for this. For some unknown reason, the launch file text simply does not appear in the post despite typing. So I am going to attach a screenshot instead.

 ![Temp_ROS_Problem](https://get-help.robotigniteacademy.com/uploads/default/original/2X/e/ef876b66a7d61bc0bc0b329526d2d9543f9964f0.jpeg)

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**Author:** ![albertoezquerro](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/albertoezquerro/32/7031_2.png) [@albertoezquerro](https://get-help.theconstruct.ai/u/albertoezquerro)\
**Post date:** [October 18, 2023, 10:49am UTC](https://get-help.theconstruct.ai/t/unable-to-launch-ros-package-exercise-3-1/26799/6 "2023-10-18T10:49:22Z")

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Hello @asghar.arafat ,

I just tested your launch file and it worked OK for me, so I understand you were able to solve this issue.

 ![Captura de Pantalla 2023-10-18 a las 12.47.59](https://get-help.robotigniteacademy.com/uploads/default/original/2X/7/719d0e752878ce93f489c81085b284b1ba16647d.png)

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**Author:** ![system](https://get-help.theconstruct.ai/uploads/default/original/2X/9/9d3ce8305cc0d0d9b6e07d15767a6f245c526f1b.jpeg) [@system](https://get-help.theconstruct.ai/u/system)\
**Post date:** [October 23, 2023, 10:49am UTC](https://get-help.theconstruct.ai/t/unable-to-launch-ros-package-exercise-3-1/26799/7 "2023-10-23T10:49:34Z")

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