You need to update your system:

sudo apt update
sudo apt upgrade
sudo apt install gcc

You'll have to completely purge what you have and perform a fresh install.

Much of this is done automatically when using the GUI. But when using the commandline you have to be specific to remove the leftover packages and other files manually.

First completely purge/remove what you currently have installed, which isn't working. Clean and update your repository cache and packages, then freshly install gcc.

$ sudo apt purge gcc
$ sudo apt-get autoremove
$ sudo apt update
$ sudo apt upgrade
$ sudo apt full-upgrade
$ sudo apt install gcc

Check for errors between commands. There shouldn't be errors. If they are, address the suggested remedy provided to fix the error. For instance, there might be an occasional warning or error such as:

E: dpkg was interrupted, you must manually run 'sudo dpkg --configure -a' to correct the problem.

To resolve that particular state, run:

$ sudo dpkg --configure -a

Then after fixing that part, proceed to the next step.

Each of the commands should give a clean state. You'll then have a fresh install from the repository.

If sudo apt-get update does not work for you, you should maybe try sudo apt-get clean to clean the cache and then execute sudo apt-get update

I was able to install GCC with sudo apt install gcc

if that doesn't work try upgrading your packages.

I found the YouTube video at https://www.systranbox.com/how-to-install-gcc-on-wsl-linux/ somewhat helpful in that regard.

Is GCC-4.8 available for 12.04 Precise now?

Update: As of 6/05/2013, there is currently a release of gcc 4.8.1 for 12.04(precise) available at https://launchpad.net/~ubuntu-toolchain-r/+archive/test.

The short answer is: gcc-4.8 is currently available for 12.04(Precise) via the toolchain PPA or by compiling the source(see below for details).

Release Announcement

The announcement for the release of gcc-4.8 was made on March 22nd, so you probably won't be seeing this in an official repository just yet.

However, it appears that Launchpad does have a PPA available for the toolchain test builds that does include gcc-4.8, here: https://launchpad.net/~ubuntu-toolchain-r/+archive/test

According to the changelog and package list, there are debs for i386, amd64, arm, and powerpc and were built against raring 13.04.

The latest available version of gcc, for 12.04, is 4.8.1 and is available in the toolchain PPA.

Adding the toolchain/test PPA:

To add the PPA to your system, open a terminal(Ctrl+Alt+t) and run the following commands:

sudo apt-get install python-software-properties
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt-get update
sudo apt-get install gcc-4.8
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.8 50

You will also be prompted to install a number of suggested packages. These packages are recommended, but optional, for the installation of gcc-4.8.

• What are PPAs and how do I use them?
• Are PPA's safe to add to my system and what are some "red flags" to watch out for?

What C++ features are available in gcc-4.8 that are not available in gcc-4.7.2?

• According to GNU.ORG, gcc-4.7, supports a number of C++11 features.

• As of the gcc-4.8 release, gcc-4.7 does not support 8 out of 64 features (See C++0x/C++11 Support in GCC)

• These features are:

  Language Features
  - Rvalue references for *this
  - Generalized attributes
  - Alignment support
  - Inheriting constructors
  Concurreny
  - Bidirectional Fences
  - Memory model
  - Abandoning a process and at_quick_exit
  - Thread-local storage 
  

• For a full list of changes in gcc-4.8, see the Changelist

I need these gcc features on 12.04 Precise, now. How can I get them?

Building GCC-4.8 from source:

If you need gcc-4.8 on 12.04 now, your only option is to build it from source.

Please read the GCC installation FAQ prior to installation.

You can download gcc-4.8 from one of gnu.org's mirror sites or directly from their SVN server.

Here is an example of steps to compile from source (see here for additional details.) Note that these may vary depending on your system and preferences.

1. Download the source code

   • Make a build directory ( mkdir gcc-build && cd gcc-build)
   • Download the source file: wget http://www.netgull.com/gcc/releases/gcc-4.8.0/gcc-4.8.0.tar.bz2 (adjust this command to use an appropriate mirror site.
   • Unzip the file (tar -xvjf <file name>)

2. Install some additional libraries (sudo apt-get install libgmp-dev libmpfr-dev libmpc-dev libc6-dev)

3. Compile the source: ./gcc-4.8.0/configure --prefix=/app/gcc/4.8.0
4. Run make (This will take some time to complete. Go make some coffee, or bake some cookies. ;-))
5. Install the code: sudo make install

Once this process has completed, run the command gcc --version to verify that the installation has completed successfully. You should see something similar to the following output:

maggotbrain@foucault:~$ gcc --version
gcc (Linaro 4.8.0) 4.8.0
Copyright (C) 2013 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

The bottom line: Thank all those folks who provide easy to install Ubuntu backports for you. Give them some of the cookies that you baked while running make. ;-)

As some comments have already pointed out, gcc is part of the main ubuntu repository. So technically, there should be a package gcc. You can search for all the packages that are available by running the command

apt-cache search gcc

This will show all packages that have gcc in their name (and that will likely be very many). You can narrow down the search to packages that start with gcc and then have a space (in other words, the package that really is called gcc),

apt-cache search gcc | grep "^gcc[[:space:]]"

If the former command found packages such as gcc-8 or similar, but the latter command didn't show anything, then it is likely that your package management doesn't know about gcc. Some comments have also suggested to update the package database by running

sudo apt-get update

This is generally a good idea before you install packages, because the installation will attempt to download whatever you try to install and that download may fail if (for example) the location of the package has changed. The command apt-get update makes sure everything is in the right place so that things can be found when you want to install them.

If after updating your package database (by apt-get update), you still don't find a package called gcc, but you do find one with a specific version number, the simplest way to get you a working gcc on your computer is probably to settle for a specific version, such as for example by running

sudo apt-get install gcc-7

You may have seen that some comments have pointed out that gcc would normally be part of an ubuntu installation. So the errors you are reporting might point at some more intricate problem with they way your package database is configured. If you are on a freshly installed ubuntu system, the simplest way to fix this is to simply re-install your system while you have a solid internet connection. If you are not on a freshly installed ubuntu system, things can be a bit more involved, but they are quite well documented if you search for ways to fix your /etc/apt/sources.list file.

Tested on Ubuntu 20.04:

sudo add-apt-repository ppa:ubuntu-toolchain-r/ppa
sudo apt update
sudo apt install g++-10

In the message, we clearly see that libstdc++6-4.7-dev_4.7.3-1ubuntu1_amd64 is a directory and not a file in your case.

So you have to provide a file.

To answer your question, when I installed Ubuntu for the first time, I found the gcc already installed

I just typed gcc -v and i got:

gcc version 4.8.4 (Ubuntu 4.8.4-2ubuntu1~14.04) 

If for any reason you don't have access to gcc and in order to install it in ubuntu, you will need the build-essential package.

Build-essential contains a list of packages which are essential for building Ubuntu packages including gcc compiler, make and other required tools.

Just go like this:

$ sudo apt-get update
$ sudo apt-get upgrade
$ sudo apt-get install build-essential

Look at this page you will get instructions to install gcc.

After doing so, you will have access to gcc and g++ compilers

There's a metapackage called build-essential which should install the compiler and a bunch of related/needed packages:

sudo apt-get install build-essential

The suggestion to first do sudo apt-get update is sound, this will update package lists and all versions should match nicely.

That is, however, if you didn't modify your /etc/apt/sources.list file manually. If so, then maybe some of the changes you made or repositories you added contain conflicting packages which cause the problems you see. If that's the case, please look at the file and fix the troublesome entries. Of course, if you want help doing so, you can post your sources.list file (or any fragments in /etc/apt/sources.list.d) and maybe someone can help you fix them.

Vijay's comment fixed my problem. Thank you Vijay.

The answer is here.

That particular error message may indicate that you have held packages, but it may also indicate a different problem.

You can get a list of actual held packages with:

dpkg --get-selections | grep hold

If there are none, or none look related, then it's probably something else. Check carefully the output of the command you were trying when you got the error message, as there may be other clues in the full output from that command, aside from the error message.

Another method of troubleshooting may be to use aptitude rather than apt-get to try to install your package:

sudo aptitude install gcc

Aptitude will give up less easily, and will attempt to find solutions which may involve modifying other packages. It may give you more explanation of the problem and options for fixing it.

Occasionally aptitude will be too eager to remove or downgrade large numbers of packages to satisfy your request, in which case retrying with -f changes its priorities and helps it come up with solutions that involve removing/downgrading fewer packages even if it means not all changes you requested can go ahead:

sudo aptitude -f install gcc

The last two options fixed my problem, i hope that it helps someone else too.

gcc-12 is not available in ubuntu 20.04, so we need to compile it from source code, here are the steps which I borrowed from this video:

• Step 1: clone gcc source code and checkout gcc-12 branch

$ git clone https://gcc.gnu.org/git/gcc.git gcc-source
$ cd gcc-source/
$ git branch -a
$ git checkout remotes/origin/releases/gcc-12

• Step 2: make another build dir

Note this is important as running ./configure from within the source directory is not supported as documented here.

$ mkdir ../gcc-12-build
$ cd ../gcc-12-build/
$ ./../gcc-source/configure --prefix=$HOME/install/gcc-12 --enable-languages=c,c++

• Step 3: installing GCC prequisites and run configure again

The missing libraries will be shown in above ./confgiure output, search and install them one by one.

$ apt-cache search MPFR
$ sudo apt-get install libmpfrc++-dev
$ apt-cache search MPC | grep dev
$ sudo apt-get install libmpc-dev
$ apt-cache search GMP | grep dev
$ sudo apt-get install libgmp-dev
$ sudo apt-get install gcc-multilib
$ ./../gcc-source/configure --prefix=$HOME/install/gcc-12 --enable-languages=c,c++

An alternative is to run the download_prerequisites script.

$ cd ../
$ cd gcc-source/
$ ./contrib/download_prerequisites
$ ./../gcc-source/configure --prefix=$HOME/install/gcc-12 --enable-languages=c,c++

• Step 4: compile gcc-12

$ make -j16

Still flex is missing:

$ sudo apt-get install flex
$ ./../gcc-source/configure --prefix=$HOME/install/gcc-12 --enable-languages=c,c++
$ make -j16
$ make install

Another way is to use Ubuntu 22.04 where gcc-12 is available. In Ubuntu 22.04, gcc-12 can be installed with apt:

$ sudo apt install gcc-12

You need to:

1. Update and upgrade:

$ sudo apt-get update && sudo apt-get upgrade -y

2.Clean unrequired packages:

$ sudo apt autoremove -y

3. Install GCC:

$ sudo apt-get install gcc -y

4. Check and confirmed installed gcc version:

gcc --version

To install gcc-7 on ubuntu you should use this ppa:

sudo add-apt-repository ppa:jonathonf/gcc
sudo apt-get update

Then run: apt-cache search gcc-7

sample output :

gcc-7-base - GCC, the GNU Compiler Collection (base package)
gcc-7 - GNU C compiler
gcc-7-multilib - GNU C compiler (multilib support)
gcc-7-plugin-dev - Files for GNU GCC plugin development.
gcc-7-test-results - Test results for the GCC test suite
lib32gcc-7-dev - GCC support library (32 bit development files)
libgcc-7-dev - GCC support library (development files)
gcc-7-doc - Documentation for the GNU compilers (gcc, gobjc, g++)
gcc-7-hppa64-linux-gnu - GNU C compiler (cross compiler for hppa64)
gcc-7-locales - GCC, the GNU compiler collection (native language support files)
gcc-7-source - Source of the GNU Compiler Collection
libx32gcc-7-dev - GCC support library (x32 development files)
gcc-7-offload-nvptx - GCC offloading compiler to NVPTX
lib64gcc-7-dev - GCC support library (64bit development files)

Install gcc-7:

sudo apt install gcc-7

I wanted to install gcc-6 alongside my existing installation of gcc-9 and this is how I did it. First off, sudo apt install gcc-6 didn't work because the package wasn't found so I had to add a new repository that contained gcc-6. To do this, I first found a repository that contains gcc-6 from Google and ended up at: https://packages.ubuntu.com/bionic/gcc-6

From there, I chose an architecture (amd64) which took me to a page with all the mirrors. I added the first mirror (mirrors.kernel.org/ubuntu) to /etc/apt/sources.list and did sudo apt update and then installed gcc-6 with sudo apt install gcc-6.

To switch between gcc versions, I used the following:

sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-6 6
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-9 9

sudo update-alternatives --config g++