How to detect whether tomcat and ant are installed

问题:

I am trying to install Tomcat and Ant on my linux machine, but before installing them i just need to check whether they are already installed or not.

Regarding tomcat:

I googled a lot and searched on my machine in the following directories for tomcat

/usr/local/, /opt/, /usr/share/

but i din't find tomcat folder in any of the above path, whether it indicates that tomcat is not installed ? so actually

1. what is the path to `look/find` exactly to know/check whether tomcat is installed or not in 
   all linux machines
2. what will be the path the tomcat will be installed exactly after installation
3. How to find the version of tomcat on any linux machine (if tomcat already installed) 
4. Whether there are any commands to look for both whether `tomcat` installed and `ant` 
   installed

Regarding Ant:

I googled and got the below command due to which i got the below result after executing it

sh-4.2$ ant -v

result

sh-4.2$ ant -v
Apache Ant(TM) version 1.8.2 compiled on November 21 2011
Trying the default build file: build.xml
Buildfile: build.xml does not exist!
Build failed

so actually

1. Does the above result mean that `Ant` is installed ? or not ?
2. what is the path to `look/find` exactly to know/check whether ant is installed or not in 
   all linux machines
3. what will be the path the `ant` will be installed exactly after installation
4. How to find the version of `Ant` on any linux machine (if Ant already installed) 

回答1:

Generally, you can check whether they are on the $PATH, if they are not on the $PATH, install one.

For ant:

ant -v stands for verbose, ant -version prints out its version.

   -help, -h
          print help on the command line options

   -projecthelp, -p
          gives information on possible targets for this project

   -version
          prints the version number and then exits ant

   -quiet, -q
          be extra quiet

   -verbose, -v
          be extra verbose

   -debug, -d
          print debugging information

   -emacs, -e
          produce logging information without adornments

   -logfile <file>, -l <file>
          use the given file to output log to

   -logger <classname>
          the class which is to perform logging

   -listener <classname>
          add an instance of the given class as a project listener

   -noinput
          do not allow interactive input

   -buildfile <file>, -file <file>, -f <file>
          use  the  given buildfile instead of the default build.xml file.
          This is the ant equivalent of Makefile

   -D<property>=<value>
          use value for the given property

   -keep-going, -k
          execute all targets that do not depend on failed target(s)

   -propertyfile <file>
          load all properties from file with -D properties  taking  prece-
          dence

   -inputhandler <class>
          the class which will handle input requests

   -find <file>, -s <file>
          (s)earch  for  buildfile  towards the root of the filesystem and
          use it

   -nice number
          A niceness value for the main thread: 1 (lowest)  to  10  (high-
          est); 5 is the default

   -nouserlib
          Run ant without using the jar files from ${user.home}/.ant/lib

   -noclasspath
          Run ant without using CLASSPATH

   -autoproxy
          Java 1.5+ : use the OS proxies

   -main <class>
          override ant's normal entry point

For tomcat:

if tomcat/bin is on the $PATH variable, version.sh will print out the version.

回答2:

For linux ubuntu 18.04:

Go to terminal and command:$ sudo systemctl status tomcat

This command also show is tomcat running or not (if already installed)