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How to choose the default gcc and g++ version?
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So I have installed gcc-4.4 and gcc-4.3 (same for g++). Now as far as I remember there is a tool in Ubuntu which sets the symlinks for you if you just tell it which version you want. However it does not seem to work in the newest version, which I find disappointing.
root@nexus:~# update-alternatives --config gcc
update-alternatives: error: no alternatives for gcc.
root@nexus:~# update-alternatives --config cc
There is only one alternative in link group cc: /usr/bin/gcc
Nothing to configure.
root@nexus:~# dpkg -l | grep gcc | awk '{print $2}'
gcc
gcc-4.3
gcc-4.3-base
gcc-4.3-multilib
gcc-4.4
gcc-4.4-base
gcc-4.4-multilib
gcc-4.5-base
gcc-multilib
lib32gcc1
libgcc1
Any ideas?
gcc g++
add a comment |
So I have installed gcc-4.4 and gcc-4.3 (same for g++). Now as far as I remember there is a tool in Ubuntu which sets the symlinks for you if you just tell it which version you want. However it does not seem to work in the newest version, which I find disappointing.
root@nexus:~# update-alternatives --config gcc
update-alternatives: error: no alternatives for gcc.
root@nexus:~# update-alternatives --config cc
There is only one alternative in link group cc: /usr/bin/gcc
Nothing to configure.
root@nexus:~# dpkg -l | grep gcc | awk '{print $2}'
gcc
gcc-4.3
gcc-4.3-base
gcc-4.3-multilib
gcc-4.4
gcc-4.4-base
gcc-4.4-multilib
gcc-4.5-base
gcc-multilib
lib32gcc1
libgcc1
Any ideas?
gcc g++
1
As @Oli explained, this is a bad idea. Debian-devel mail list: "I don't think alternatives should be used for versioning. For example, we don't use alternatives for gcc, neither for Python." lists.debian.org/debian-devel/2014/06/msg00381.html
– hmijail
Aug 18 '16 at 20:39
OK, so what do you use for versioning?
– WillC
Nov 28 '18 at 8:34
add a comment |
So I have installed gcc-4.4 and gcc-4.3 (same for g++). Now as far as I remember there is a tool in Ubuntu which sets the symlinks for you if you just tell it which version you want. However it does not seem to work in the newest version, which I find disappointing.
root@nexus:~# update-alternatives --config gcc
update-alternatives: error: no alternatives for gcc.
root@nexus:~# update-alternatives --config cc
There is only one alternative in link group cc: /usr/bin/gcc
Nothing to configure.
root@nexus:~# dpkg -l | grep gcc | awk '{print $2}'
gcc
gcc-4.3
gcc-4.3-base
gcc-4.3-multilib
gcc-4.4
gcc-4.4-base
gcc-4.4-multilib
gcc-4.5-base
gcc-multilib
lib32gcc1
libgcc1
Any ideas?
gcc g++
So I have installed gcc-4.4 and gcc-4.3 (same for g++). Now as far as I remember there is a tool in Ubuntu which sets the symlinks for you if you just tell it which version you want. However it does not seem to work in the newest version, which I find disappointing.
root@nexus:~# update-alternatives --config gcc
update-alternatives: error: no alternatives for gcc.
root@nexus:~# update-alternatives --config cc
There is only one alternative in link group cc: /usr/bin/gcc
Nothing to configure.
root@nexus:~# dpkg -l | grep gcc | awk '{print $2}'
gcc
gcc-4.3
gcc-4.3-base
gcc-4.3-multilib
gcc-4.4
gcc-4.4-base
gcc-4.4-multilib
gcc-4.5-base
gcc-multilib
lib32gcc1
libgcc1
Any ideas?
gcc g++
gcc g++
edited May 30 '18 at 8:59
Ciro Santilli 新疆改造中心996ICU六四事件
10.6k45054
10.6k45054
asked Feb 15 '11 at 15:52
NilsNils
1,111389
1,111389
1
As @Oli explained, this is a bad idea. Debian-devel mail list: "I don't think alternatives should be used for versioning. For example, we don't use alternatives for gcc, neither for Python." lists.debian.org/debian-devel/2014/06/msg00381.html
– hmijail
Aug 18 '16 at 20:39
OK, so what do you use for versioning?
– WillC
Nov 28 '18 at 8:34
add a comment |
1
As @Oli explained, this is a bad idea. Debian-devel mail list: "I don't think alternatives should be used for versioning. For example, we don't use alternatives for gcc, neither for Python." lists.debian.org/debian-devel/2014/06/msg00381.html
– hmijail
Aug 18 '16 at 20:39
OK, so what do you use for versioning?
– WillC
Nov 28 '18 at 8:34
1
1
As @Oli explained, this is a bad idea. Debian-devel mail list: "I don't think alternatives should be used for versioning. For example, we don't use alternatives for gcc, neither for Python." lists.debian.org/debian-devel/2014/06/msg00381.html
– hmijail
Aug 18 '16 at 20:39
As @Oli explained, this is a bad idea. Debian-devel mail list: "I don't think alternatives should be used for versioning. For example, we don't use alternatives for gcc, neither for Python." lists.debian.org/debian-devel/2014/06/msg00381.html
– hmijail
Aug 18 '16 at 20:39
OK, so what do you use for versioning?
– WillC
Nov 28 '18 at 8:34
OK, so what do you use for versioning?
– WillC
Nov 28 '18 at 8:34
add a comment |
6 Answers
6
active
oldest
votes
First erased the current update-alternatives setup for gcc and g++:
sudo update-alternatives --remove-all gcc
sudo update-alternatives --remove-all g++
Install Packages
It seems that both gcc-4.3 and gcc-4.4 are installed after install build-essential. However, we can explicitly install the following packages:
sudo apt-get install gcc-4.3 gcc-4.4 g++-4.3 g++-4.4
Install Alternatives
Symbolic links cc and c++ are installed by default. We will install symbol links for gcc and g++, then link cc and c++ to gcc and g++ respectively. (Note that the 10
, 20
and 30
options are the priorities for each alternative.)
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.3 10
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.4 20
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.3 10
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.4 20
sudo update-alternatives --install /usr/bin/cc cc /usr/bin/gcc 30
sudo update-alternatives --set cc /usr/bin/gcc
sudo update-alternatives --install /usr/bin/c++ c++ /usr/bin/g++ 30
sudo update-alternatives --set c++ /usr/bin/g++
Configure Alternatives
The last step is configuring the default commands for gcc, g++. It's easy to switch between 4.3 and 4.4 interactively:
sudo update-alternatives --config gcc
sudo update-alternatives --config g++
Or switch using script:
#!/bin/sh
if [ -z "$1" ]; then
echo "usage: $0 version" 1>&2
exit 1
fi
if [ ! -f "/usr/bin/gcc-$1" ] || [ ! -f "/usr/bin/g++-$1" ]; then
echo "no such version gcc/g++ installed" 1>&2
exit 1
fi
update-alternatives --set gcc "/usr/bin/gcc-$1"
update-alternatives --set g++ "/usr/bin/g++-$1"
4
Thx, so you have to add them manually to update-alternatives.. IIRC earlier Ubuntu versions did that automatically.
– Nils
Feb 15 '11 at 19:33
1
This is especially useful to me when compiling nvidia modules for different kernels. Thank you so much for explaining update-alternatives
– earthmeLon
Apr 15 '12 at 10:57
1
Thank you! I used your other answer to update from 4.6 to 4.7. I wanted to use this answer, but I was not sure why do you put numbers like 10 20 30 after some of you commands. Could you please explain?
– Martin Drozdik
Dec 28 '12 at 22:02
7
The numbers are priorities as it turns out, according to the manpage. I imagine in the case that one of the version is uninstalled it will use those priorities to determine which one should become the new default.
– Ibrahim
Jan 14 '13 at 20:04
1
@Ibrahim: No, they determine what gets chosen when you select auto mode
– Cookie
Mar 24 '14 at 16:25
|
show 5 more comments
execute in terminal :
gcc -v
g++ -v
Okay, so that part is fairly simple. The tricky part is that when you issue the command GCC it is actually a sybolic link to which ever version of GCC you are using. What this means is we can create a symbolic link from GCC to whichever version of GCC we want.
- You can see the symbolic link :
ls -la /usr/bin | grep gcc-4.4
ls -la /usr/bin | grep g++-4.4
- So what we need to do is remove the GCC symlink and the G++ symlink and then recreate them linked to GCC 4.3 and G++ 4.3:
rm /usr/bin/gcc
rm /usr/bin/g++
ln -s /usr/bin/gcc-4.3 /usr/bin/gcc
ln -s /usr/bin/g++-4.3 /usr/bin/g++
- Now if we check the symbolic links again we will see GCC & G++ are now linked to GCC 4.3 and G++ 4.3:
ls -la /usr/bin/ | grep gcc
ls -la /usr/bin/ | grep g++
- Finally we can check our GCC -v again and make sure we are using the correct version:
gcc -v
g++ -v
Exactly what I was looking for! Forgot about the ability to symlink "gcc" to whatever version I have installed. Thanks!
– CalebHC
Mar 1 at 18:01
add a comment |
Is this really desirable? There are ABI changes between gcc
versions. Compiling something with one version (eg the entire operating system) and then compiling something else with another version, can cause conflict.
For example, kernel modules should always be compiled with the same version of gcc
used to compile the kernel. With that in mind, if you manually altered the symlink between /usr/bin/gcc
and the version used in your version of Ubuntu, future DKMS-built modules might use the wrong gcc
version.
If you just want to build things with a different version of gcc
, that's easy enough, even with makescripts. For example, you can pass in the version of gcc
in the CC
environment variable:
CC="gcc-4.5" ./configure
CC="gcc-4.5" make
You might not need it on the make command (configure scripts usually pull it in) but it doesn't hurt.
Thx for your comment. I'm aware of the CC variable, but this was not really the question.
– Nils
Feb 15 '11 at 16:31
2
True enough but I have explained whygcc
isn't part of thealternatives
system and why this isn't particularly desirable. If neither of those are going to change your mind, just do it manually.
– Oli♦
Feb 15 '11 at 16:43
It was before? Now they just removed it?! Compiling (userspace) software with different gcc versions should be perfectly ok.. this discussion is getting sill..
– Nils
Feb 15 '11 at 18:12
Can you explain why per-invocation environment variables are preferable to a system-wide configuration setting?$ sudo apt-get install gcc-6 gcc-7 $ CC="gcc-7" ./configure <much output> $ make # uses gcc-7
Whereassudo update-alternatives gcc gcc-7
would have made sure that you don't accidentally switch ABIs.
– kfsone
Jun 12 '17 at 22:01
add a comment |
Edit:
This assumes that you have installed the version first, with e.g.:
sudo apt install gcc-4.9 g++-4.9
Original:
And here is a one-liner for those who are lazy, just change change the number at the end to the version you want. It will make the change for gcc and/or g++
ls -la /usr/bin/ | grep -oP "[S]*(gcc|g++)(-[a-z]+)*[s]" | xargs bash -c 'for link in ${@:1}; do sudo ln -s -f "/usr/bin/${link}-${0}" "/usr/bin/${link}"; done' 4.9
In this example I switched to 4.9
There are no error checks and what not in this example, so you might want to check what will be run before you run it. Just add echo before sudo. For completeness I provide check line as well:
ls -la /usr/bin/ | grep -oP "[S]*(gcc|g++)(-[a-z]+)*[s]" | xargs bash -c 'for link in ${@:1}; do echo sudo ln -s -f "/usr/bin/${link}-${0}" "/usr/bin/${link}"; done' 4.9
The output from the check should be something like:
sudo ln -s -f /usr/bin/g++-4.9 /usr/bin/g++
sudo ln -s -f /usr/bin/gcc-4.9 /usr/bin/gcc
sudo ln -s -f /usr/bin/gcc-ar-4.9 /usr/bin/gcc-ar
sudo ln -s -f /usr/bin/gcc-nm-4.9 /usr/bin/gcc-nm
sudo ln -s -f /usr/bin/gcc-ranlib-4.9 /usr/bin/gcc-ranlib
sudo ln -s -f /usr/bin/x86_64-linux-gnu-g++-4.9 /usr/bin/x86_64-linux-gnu-g++
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-4.9 /usr/bin/x86_64-linux-gnu-gcc
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-ar-4.9 /usr/bin/x86_64-linux-gnu-gcc-ar
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-nm-4.9 /usr/bin/x86_64-linux-gnu-gcc-nm
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-ranlib-4.9 /usr/bin/x86_64-linux-gnu-gcc-ranlib
You can check the version after with:
gcc --version
Semi-detailed explanation:
ls -la /usr/bin/ lists all files in /usr/bin
| pipe (send) the output to the next command
grep -oP matches the search regex per line. o only shows the result not the entire matched line. P tells grep to use perl-regex. I will not go into regex here, read up on it if you want to.
xargs simply put, it gathers the results that are piped to it and send all of them to the end. i.e. to the command following xargs
bash well, it's bash. The c flag tells it to use the string as a command. In this example it loops over the arguments sent from xargs by skipping the first (0th) argument, in this case the loop skips 4.9. The 0th argument is used in the loop to change the link.
ln -s -f The s flag makes a symbolic link, f forces unlinking first if needed.
2
Very old question, but this answer seems to be one of the gems we should look for when reviewing answers to old posts...
– mook765
Oct 16 '16 at 7:12
Brilliant! Best answer hands down!
– Gabriel Staples
Jan 15 '18 at 4:04
add a comment |
Consider one way upgrade:
sudo apt install gcc-7
sudo apt remove gcc-5
apt will handle links staff automatically in this case. New C/C++ version is pretty compatible. You hardly would ever need old one.
1
This did not work on Ubuntu 18.04 and gcc-7 and gcc-8. After the removal of gcc-7 there is no link forgcc
.
– Werner Henze
Jan 11 at 11:03
@WernerHenze, in this case you also may need to reinstall g++ package which will update-alternatives for you.
– Sergei
Feb 15 at 11:40
add a comment |
How about a symbolic link in a temporary directory:
mkdir x && PATH=$PWD/x:$PATH && ln -s /usr/bin/g++-7 $PWD/x/g++
add a comment |
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6 Answers
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6 Answers
6
active
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active
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oldest
votes
First erased the current update-alternatives setup for gcc and g++:
sudo update-alternatives --remove-all gcc
sudo update-alternatives --remove-all g++
Install Packages
It seems that both gcc-4.3 and gcc-4.4 are installed after install build-essential. However, we can explicitly install the following packages:
sudo apt-get install gcc-4.3 gcc-4.4 g++-4.3 g++-4.4
Install Alternatives
Symbolic links cc and c++ are installed by default. We will install symbol links for gcc and g++, then link cc and c++ to gcc and g++ respectively. (Note that the 10
, 20
and 30
options are the priorities for each alternative.)
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.3 10
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.4 20
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.3 10
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.4 20
sudo update-alternatives --install /usr/bin/cc cc /usr/bin/gcc 30
sudo update-alternatives --set cc /usr/bin/gcc
sudo update-alternatives --install /usr/bin/c++ c++ /usr/bin/g++ 30
sudo update-alternatives --set c++ /usr/bin/g++
Configure Alternatives
The last step is configuring the default commands for gcc, g++. It's easy to switch between 4.3 and 4.4 interactively:
sudo update-alternatives --config gcc
sudo update-alternatives --config g++
Or switch using script:
#!/bin/sh
if [ -z "$1" ]; then
echo "usage: $0 version" 1>&2
exit 1
fi
if [ ! -f "/usr/bin/gcc-$1" ] || [ ! -f "/usr/bin/g++-$1" ]; then
echo "no such version gcc/g++ installed" 1>&2
exit 1
fi
update-alternatives --set gcc "/usr/bin/gcc-$1"
update-alternatives --set g++ "/usr/bin/g++-$1"
4
Thx, so you have to add them manually to update-alternatives.. IIRC earlier Ubuntu versions did that automatically.
– Nils
Feb 15 '11 at 19:33
1
This is especially useful to me when compiling nvidia modules for different kernels. Thank you so much for explaining update-alternatives
– earthmeLon
Apr 15 '12 at 10:57
1
Thank you! I used your other answer to update from 4.6 to 4.7. I wanted to use this answer, but I was not sure why do you put numbers like 10 20 30 after some of you commands. Could you please explain?
– Martin Drozdik
Dec 28 '12 at 22:02
7
The numbers are priorities as it turns out, according to the manpage. I imagine in the case that one of the version is uninstalled it will use those priorities to determine which one should become the new default.
– Ibrahim
Jan 14 '13 at 20:04
1
@Ibrahim: No, they determine what gets chosen when you select auto mode
– Cookie
Mar 24 '14 at 16:25
|
show 5 more comments
First erased the current update-alternatives setup for gcc and g++:
sudo update-alternatives --remove-all gcc
sudo update-alternatives --remove-all g++
Install Packages
It seems that both gcc-4.3 and gcc-4.4 are installed after install build-essential. However, we can explicitly install the following packages:
sudo apt-get install gcc-4.3 gcc-4.4 g++-4.3 g++-4.4
Install Alternatives
Symbolic links cc and c++ are installed by default. We will install symbol links for gcc and g++, then link cc and c++ to gcc and g++ respectively. (Note that the 10
, 20
and 30
options are the priorities for each alternative.)
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.3 10
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.4 20
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.3 10
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.4 20
sudo update-alternatives --install /usr/bin/cc cc /usr/bin/gcc 30
sudo update-alternatives --set cc /usr/bin/gcc
sudo update-alternatives --install /usr/bin/c++ c++ /usr/bin/g++ 30
sudo update-alternatives --set c++ /usr/bin/g++
Configure Alternatives
The last step is configuring the default commands for gcc, g++. It's easy to switch between 4.3 and 4.4 interactively:
sudo update-alternatives --config gcc
sudo update-alternatives --config g++
Or switch using script:
#!/bin/sh
if [ -z "$1" ]; then
echo "usage: $0 version" 1>&2
exit 1
fi
if [ ! -f "/usr/bin/gcc-$1" ] || [ ! -f "/usr/bin/g++-$1" ]; then
echo "no such version gcc/g++ installed" 1>&2
exit 1
fi
update-alternatives --set gcc "/usr/bin/gcc-$1"
update-alternatives --set g++ "/usr/bin/g++-$1"
4
Thx, so you have to add them manually to update-alternatives.. IIRC earlier Ubuntu versions did that automatically.
– Nils
Feb 15 '11 at 19:33
1
This is especially useful to me when compiling nvidia modules for different kernels. Thank you so much for explaining update-alternatives
– earthmeLon
Apr 15 '12 at 10:57
1
Thank you! I used your other answer to update from 4.6 to 4.7. I wanted to use this answer, but I was not sure why do you put numbers like 10 20 30 after some of you commands. Could you please explain?
– Martin Drozdik
Dec 28 '12 at 22:02
7
The numbers are priorities as it turns out, according to the manpage. I imagine in the case that one of the version is uninstalled it will use those priorities to determine which one should become the new default.
– Ibrahim
Jan 14 '13 at 20:04
1
@Ibrahim: No, they determine what gets chosen when you select auto mode
– Cookie
Mar 24 '14 at 16:25
|
show 5 more comments
First erased the current update-alternatives setup for gcc and g++:
sudo update-alternatives --remove-all gcc
sudo update-alternatives --remove-all g++
Install Packages
It seems that both gcc-4.3 and gcc-4.4 are installed after install build-essential. However, we can explicitly install the following packages:
sudo apt-get install gcc-4.3 gcc-4.4 g++-4.3 g++-4.4
Install Alternatives
Symbolic links cc and c++ are installed by default. We will install symbol links for gcc and g++, then link cc and c++ to gcc and g++ respectively. (Note that the 10
, 20
and 30
options are the priorities for each alternative.)
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.3 10
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.4 20
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.3 10
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.4 20
sudo update-alternatives --install /usr/bin/cc cc /usr/bin/gcc 30
sudo update-alternatives --set cc /usr/bin/gcc
sudo update-alternatives --install /usr/bin/c++ c++ /usr/bin/g++ 30
sudo update-alternatives --set c++ /usr/bin/g++
Configure Alternatives
The last step is configuring the default commands for gcc, g++. It's easy to switch between 4.3 and 4.4 interactively:
sudo update-alternatives --config gcc
sudo update-alternatives --config g++
Or switch using script:
#!/bin/sh
if [ -z "$1" ]; then
echo "usage: $0 version" 1>&2
exit 1
fi
if [ ! -f "/usr/bin/gcc-$1" ] || [ ! -f "/usr/bin/g++-$1" ]; then
echo "no such version gcc/g++ installed" 1>&2
exit 1
fi
update-alternatives --set gcc "/usr/bin/gcc-$1"
update-alternatives --set g++ "/usr/bin/g++-$1"
First erased the current update-alternatives setup for gcc and g++:
sudo update-alternatives --remove-all gcc
sudo update-alternatives --remove-all g++
Install Packages
It seems that both gcc-4.3 and gcc-4.4 are installed after install build-essential. However, we can explicitly install the following packages:
sudo apt-get install gcc-4.3 gcc-4.4 g++-4.3 g++-4.4
Install Alternatives
Symbolic links cc and c++ are installed by default. We will install symbol links for gcc and g++, then link cc and c++ to gcc and g++ respectively. (Note that the 10
, 20
and 30
options are the priorities for each alternative.)
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.3 10
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.4 20
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.3 10
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.4 20
sudo update-alternatives --install /usr/bin/cc cc /usr/bin/gcc 30
sudo update-alternatives --set cc /usr/bin/gcc
sudo update-alternatives --install /usr/bin/c++ c++ /usr/bin/g++ 30
sudo update-alternatives --set c++ /usr/bin/g++
Configure Alternatives
The last step is configuring the default commands for gcc, g++. It's easy to switch between 4.3 and 4.4 interactively:
sudo update-alternatives --config gcc
sudo update-alternatives --config g++
Or switch using script:
#!/bin/sh
if [ -z "$1" ]; then
echo "usage: $0 version" 1>&2
exit 1
fi
if [ ! -f "/usr/bin/gcc-$1" ] || [ ! -f "/usr/bin/g++-$1" ]; then
echo "no such version gcc/g++ installed" 1>&2
exit 1
fi
update-alternatives --set gcc "/usr/bin/gcc-$1"
update-alternatives --set g++ "/usr/bin/g++-$1"
edited 10 hours ago
Olivia Stork
1074
1074
answered Feb 15 '11 at 19:05
hhlphhlp
33k1478131
33k1478131
4
Thx, so you have to add them manually to update-alternatives.. IIRC earlier Ubuntu versions did that automatically.
– Nils
Feb 15 '11 at 19:33
1
This is especially useful to me when compiling nvidia modules for different kernels. Thank you so much for explaining update-alternatives
– earthmeLon
Apr 15 '12 at 10:57
1
Thank you! I used your other answer to update from 4.6 to 4.7. I wanted to use this answer, but I was not sure why do you put numbers like 10 20 30 after some of you commands. Could you please explain?
– Martin Drozdik
Dec 28 '12 at 22:02
7
The numbers are priorities as it turns out, according to the manpage. I imagine in the case that one of the version is uninstalled it will use those priorities to determine which one should become the new default.
– Ibrahim
Jan 14 '13 at 20:04
1
@Ibrahim: No, they determine what gets chosen when you select auto mode
– Cookie
Mar 24 '14 at 16:25
|
show 5 more comments
4
Thx, so you have to add them manually to update-alternatives.. IIRC earlier Ubuntu versions did that automatically.
– Nils
Feb 15 '11 at 19:33
1
This is especially useful to me when compiling nvidia modules for different kernels. Thank you so much for explaining update-alternatives
– earthmeLon
Apr 15 '12 at 10:57
1
Thank you! I used your other answer to update from 4.6 to 4.7. I wanted to use this answer, but I was not sure why do you put numbers like 10 20 30 after some of you commands. Could you please explain?
– Martin Drozdik
Dec 28 '12 at 22:02
7
The numbers are priorities as it turns out, according to the manpage. I imagine in the case that one of the version is uninstalled it will use those priorities to determine which one should become the new default.
– Ibrahim
Jan 14 '13 at 20:04
1
@Ibrahim: No, they determine what gets chosen when you select auto mode
– Cookie
Mar 24 '14 at 16:25
4
4
Thx, so you have to add them manually to update-alternatives.. IIRC earlier Ubuntu versions did that automatically.
– Nils
Feb 15 '11 at 19:33
Thx, so you have to add them manually to update-alternatives.. IIRC earlier Ubuntu versions did that automatically.
– Nils
Feb 15 '11 at 19:33
1
1
This is especially useful to me when compiling nvidia modules for different kernels. Thank you so much for explaining update-alternatives
– earthmeLon
Apr 15 '12 at 10:57
This is especially useful to me when compiling nvidia modules for different kernels. Thank you so much for explaining update-alternatives
– earthmeLon
Apr 15 '12 at 10:57
1
1
Thank you! I used your other answer to update from 4.6 to 4.7. I wanted to use this answer, but I was not sure why do you put numbers like 10 20 30 after some of you commands. Could you please explain?
– Martin Drozdik
Dec 28 '12 at 22:02
Thank you! I used your other answer to update from 4.6 to 4.7. I wanted to use this answer, but I was not sure why do you put numbers like 10 20 30 after some of you commands. Could you please explain?
– Martin Drozdik
Dec 28 '12 at 22:02
7
7
The numbers are priorities as it turns out, according to the manpage. I imagine in the case that one of the version is uninstalled it will use those priorities to determine which one should become the new default.
– Ibrahim
Jan 14 '13 at 20:04
The numbers are priorities as it turns out, according to the manpage. I imagine in the case that one of the version is uninstalled it will use those priorities to determine which one should become the new default.
– Ibrahim
Jan 14 '13 at 20:04
1
1
@Ibrahim: No, they determine what gets chosen when you select auto mode
– Cookie
Mar 24 '14 at 16:25
@Ibrahim: No, they determine what gets chosen when you select auto mode
– Cookie
Mar 24 '14 at 16:25
|
show 5 more comments
execute in terminal :
gcc -v
g++ -v
Okay, so that part is fairly simple. The tricky part is that when you issue the command GCC it is actually a sybolic link to which ever version of GCC you are using. What this means is we can create a symbolic link from GCC to whichever version of GCC we want.
- You can see the symbolic link :
ls -la /usr/bin | grep gcc-4.4
ls -la /usr/bin | grep g++-4.4
- So what we need to do is remove the GCC symlink and the G++ symlink and then recreate them linked to GCC 4.3 and G++ 4.3:
rm /usr/bin/gcc
rm /usr/bin/g++
ln -s /usr/bin/gcc-4.3 /usr/bin/gcc
ln -s /usr/bin/g++-4.3 /usr/bin/g++
- Now if we check the symbolic links again we will see GCC & G++ are now linked to GCC 4.3 and G++ 4.3:
ls -la /usr/bin/ | grep gcc
ls -la /usr/bin/ | grep g++
- Finally we can check our GCC -v again and make sure we are using the correct version:
gcc -v
g++ -v
Exactly what I was looking for! Forgot about the ability to symlink "gcc" to whatever version I have installed. Thanks!
– CalebHC
Mar 1 at 18:01
add a comment |
execute in terminal :
gcc -v
g++ -v
Okay, so that part is fairly simple. The tricky part is that when you issue the command GCC it is actually a sybolic link to which ever version of GCC you are using. What this means is we can create a symbolic link from GCC to whichever version of GCC we want.
- You can see the symbolic link :
ls -la /usr/bin | grep gcc-4.4
ls -la /usr/bin | grep g++-4.4
- So what we need to do is remove the GCC symlink and the G++ symlink and then recreate them linked to GCC 4.3 and G++ 4.3:
rm /usr/bin/gcc
rm /usr/bin/g++
ln -s /usr/bin/gcc-4.3 /usr/bin/gcc
ln -s /usr/bin/g++-4.3 /usr/bin/g++
- Now if we check the symbolic links again we will see GCC & G++ are now linked to GCC 4.3 and G++ 4.3:
ls -la /usr/bin/ | grep gcc
ls -la /usr/bin/ | grep g++
- Finally we can check our GCC -v again and make sure we are using the correct version:
gcc -v
g++ -v
Exactly what I was looking for! Forgot about the ability to symlink "gcc" to whatever version I have installed. Thanks!
– CalebHC
Mar 1 at 18:01
add a comment |
execute in terminal :
gcc -v
g++ -v
Okay, so that part is fairly simple. The tricky part is that when you issue the command GCC it is actually a sybolic link to which ever version of GCC you are using. What this means is we can create a symbolic link from GCC to whichever version of GCC we want.
- You can see the symbolic link :
ls -la /usr/bin | grep gcc-4.4
ls -la /usr/bin | grep g++-4.4
- So what we need to do is remove the GCC symlink and the G++ symlink and then recreate them linked to GCC 4.3 and G++ 4.3:
rm /usr/bin/gcc
rm /usr/bin/g++
ln -s /usr/bin/gcc-4.3 /usr/bin/gcc
ln -s /usr/bin/g++-4.3 /usr/bin/g++
- Now if we check the symbolic links again we will see GCC & G++ are now linked to GCC 4.3 and G++ 4.3:
ls -la /usr/bin/ | grep gcc
ls -la /usr/bin/ | grep g++
- Finally we can check our GCC -v again and make sure we are using the correct version:
gcc -v
g++ -v
execute in terminal :
gcc -v
g++ -v
Okay, so that part is fairly simple. The tricky part is that when you issue the command GCC it is actually a sybolic link to which ever version of GCC you are using. What this means is we can create a symbolic link from GCC to whichever version of GCC we want.
- You can see the symbolic link :
ls -la /usr/bin | grep gcc-4.4
ls -la /usr/bin | grep g++-4.4
- So what we need to do is remove the GCC symlink and the G++ symlink and then recreate them linked to GCC 4.3 and G++ 4.3:
rm /usr/bin/gcc
rm /usr/bin/g++
ln -s /usr/bin/gcc-4.3 /usr/bin/gcc
ln -s /usr/bin/g++-4.3 /usr/bin/g++
- Now if we check the symbolic links again we will see GCC & G++ are now linked to GCC 4.3 and G++ 4.3:
ls -la /usr/bin/ | grep gcc
ls -la /usr/bin/ | grep g++
- Finally we can check our GCC -v again and make sure we are using the correct version:
gcc -v
g++ -v
edited Feb 15 '11 at 17:59
answered Feb 15 '11 at 16:49
hhlphhlp
33k1478131
33k1478131
Exactly what I was looking for! Forgot about the ability to symlink "gcc" to whatever version I have installed. Thanks!
– CalebHC
Mar 1 at 18:01
add a comment |
Exactly what I was looking for! Forgot about the ability to symlink "gcc" to whatever version I have installed. Thanks!
– CalebHC
Mar 1 at 18:01
Exactly what I was looking for! Forgot about the ability to symlink "gcc" to whatever version I have installed. Thanks!
– CalebHC
Mar 1 at 18:01
Exactly what I was looking for! Forgot about the ability to symlink "gcc" to whatever version I have installed. Thanks!
– CalebHC
Mar 1 at 18:01
add a comment |
Is this really desirable? There are ABI changes between gcc
versions. Compiling something with one version (eg the entire operating system) and then compiling something else with another version, can cause conflict.
For example, kernel modules should always be compiled with the same version of gcc
used to compile the kernel. With that in mind, if you manually altered the symlink between /usr/bin/gcc
and the version used in your version of Ubuntu, future DKMS-built modules might use the wrong gcc
version.
If you just want to build things with a different version of gcc
, that's easy enough, even with makescripts. For example, you can pass in the version of gcc
in the CC
environment variable:
CC="gcc-4.5" ./configure
CC="gcc-4.5" make
You might not need it on the make command (configure scripts usually pull it in) but it doesn't hurt.
Thx for your comment. I'm aware of the CC variable, but this was not really the question.
– Nils
Feb 15 '11 at 16:31
2
True enough but I have explained whygcc
isn't part of thealternatives
system and why this isn't particularly desirable. If neither of those are going to change your mind, just do it manually.
– Oli♦
Feb 15 '11 at 16:43
It was before? Now they just removed it?! Compiling (userspace) software with different gcc versions should be perfectly ok.. this discussion is getting sill..
– Nils
Feb 15 '11 at 18:12
Can you explain why per-invocation environment variables are preferable to a system-wide configuration setting?$ sudo apt-get install gcc-6 gcc-7 $ CC="gcc-7" ./configure <much output> $ make # uses gcc-7
Whereassudo update-alternatives gcc gcc-7
would have made sure that you don't accidentally switch ABIs.
– kfsone
Jun 12 '17 at 22:01
add a comment |
Is this really desirable? There are ABI changes between gcc
versions. Compiling something with one version (eg the entire operating system) and then compiling something else with another version, can cause conflict.
For example, kernel modules should always be compiled with the same version of gcc
used to compile the kernel. With that in mind, if you manually altered the symlink between /usr/bin/gcc
and the version used in your version of Ubuntu, future DKMS-built modules might use the wrong gcc
version.
If you just want to build things with a different version of gcc
, that's easy enough, even with makescripts. For example, you can pass in the version of gcc
in the CC
environment variable:
CC="gcc-4.5" ./configure
CC="gcc-4.5" make
You might not need it on the make command (configure scripts usually pull it in) but it doesn't hurt.
Thx for your comment. I'm aware of the CC variable, but this was not really the question.
– Nils
Feb 15 '11 at 16:31
2
True enough but I have explained whygcc
isn't part of thealternatives
system and why this isn't particularly desirable. If neither of those are going to change your mind, just do it manually.
– Oli♦
Feb 15 '11 at 16:43
It was before? Now they just removed it?! Compiling (userspace) software with different gcc versions should be perfectly ok.. this discussion is getting sill..
– Nils
Feb 15 '11 at 18:12
Can you explain why per-invocation environment variables are preferable to a system-wide configuration setting?$ sudo apt-get install gcc-6 gcc-7 $ CC="gcc-7" ./configure <much output> $ make # uses gcc-7
Whereassudo update-alternatives gcc gcc-7
would have made sure that you don't accidentally switch ABIs.
– kfsone
Jun 12 '17 at 22:01
add a comment |
Is this really desirable? There are ABI changes between gcc
versions. Compiling something with one version (eg the entire operating system) and then compiling something else with another version, can cause conflict.
For example, kernel modules should always be compiled with the same version of gcc
used to compile the kernel. With that in mind, if you manually altered the symlink between /usr/bin/gcc
and the version used in your version of Ubuntu, future DKMS-built modules might use the wrong gcc
version.
If you just want to build things with a different version of gcc
, that's easy enough, even with makescripts. For example, you can pass in the version of gcc
in the CC
environment variable:
CC="gcc-4.5" ./configure
CC="gcc-4.5" make
You might not need it on the make command (configure scripts usually pull it in) but it doesn't hurt.
Is this really desirable? There are ABI changes between gcc
versions. Compiling something with one version (eg the entire operating system) and then compiling something else with another version, can cause conflict.
For example, kernel modules should always be compiled with the same version of gcc
used to compile the kernel. With that in mind, if you manually altered the symlink between /usr/bin/gcc
and the version used in your version of Ubuntu, future DKMS-built modules might use the wrong gcc
version.
If you just want to build things with a different version of gcc
, that's easy enough, even with makescripts. For example, you can pass in the version of gcc
in the CC
environment variable:
CC="gcc-4.5" ./configure
CC="gcc-4.5" make
You might not need it on the make command (configure scripts usually pull it in) but it doesn't hurt.
answered Feb 15 '11 at 16:22
Oli♦Oli
225k91567769
225k91567769
Thx for your comment. I'm aware of the CC variable, but this was not really the question.
– Nils
Feb 15 '11 at 16:31
2
True enough but I have explained whygcc
isn't part of thealternatives
system and why this isn't particularly desirable. If neither of those are going to change your mind, just do it manually.
– Oli♦
Feb 15 '11 at 16:43
It was before? Now they just removed it?! Compiling (userspace) software with different gcc versions should be perfectly ok.. this discussion is getting sill..
– Nils
Feb 15 '11 at 18:12
Can you explain why per-invocation environment variables are preferable to a system-wide configuration setting?$ sudo apt-get install gcc-6 gcc-7 $ CC="gcc-7" ./configure <much output> $ make # uses gcc-7
Whereassudo update-alternatives gcc gcc-7
would have made sure that you don't accidentally switch ABIs.
– kfsone
Jun 12 '17 at 22:01
add a comment |
Thx for your comment. I'm aware of the CC variable, but this was not really the question.
– Nils
Feb 15 '11 at 16:31
2
True enough but I have explained whygcc
isn't part of thealternatives
system and why this isn't particularly desirable. If neither of those are going to change your mind, just do it manually.
– Oli♦
Feb 15 '11 at 16:43
It was before? Now they just removed it?! Compiling (userspace) software with different gcc versions should be perfectly ok.. this discussion is getting sill..
– Nils
Feb 15 '11 at 18:12
Can you explain why per-invocation environment variables are preferable to a system-wide configuration setting?$ sudo apt-get install gcc-6 gcc-7 $ CC="gcc-7" ./configure <much output> $ make # uses gcc-7
Whereassudo update-alternatives gcc gcc-7
would have made sure that you don't accidentally switch ABIs.
– kfsone
Jun 12 '17 at 22:01
Thx for your comment. I'm aware of the CC variable, but this was not really the question.
– Nils
Feb 15 '11 at 16:31
Thx for your comment. I'm aware of the CC variable, but this was not really the question.
– Nils
Feb 15 '11 at 16:31
2
2
True enough but I have explained why
gcc
isn't part of the alternatives
system and why this isn't particularly desirable. If neither of those are going to change your mind, just do it manually.– Oli♦
Feb 15 '11 at 16:43
True enough but I have explained why
gcc
isn't part of the alternatives
system and why this isn't particularly desirable. If neither of those are going to change your mind, just do it manually.– Oli♦
Feb 15 '11 at 16:43
It was before? Now they just removed it?! Compiling (userspace) software with different gcc versions should be perfectly ok.. this discussion is getting sill..
– Nils
Feb 15 '11 at 18:12
It was before? Now they just removed it?! Compiling (userspace) software with different gcc versions should be perfectly ok.. this discussion is getting sill..
– Nils
Feb 15 '11 at 18:12
Can you explain why per-invocation environment variables are preferable to a system-wide configuration setting?
$ sudo apt-get install gcc-6 gcc-7 $ CC="gcc-7" ./configure <much output> $ make # uses gcc-7
Whereas sudo update-alternatives gcc gcc-7
would have made sure that you don't accidentally switch ABIs.– kfsone
Jun 12 '17 at 22:01
Can you explain why per-invocation environment variables are preferable to a system-wide configuration setting?
$ sudo apt-get install gcc-6 gcc-7 $ CC="gcc-7" ./configure <much output> $ make # uses gcc-7
Whereas sudo update-alternatives gcc gcc-7
would have made sure that you don't accidentally switch ABIs.– kfsone
Jun 12 '17 at 22:01
add a comment |
Edit:
This assumes that you have installed the version first, with e.g.:
sudo apt install gcc-4.9 g++-4.9
Original:
And here is a one-liner for those who are lazy, just change change the number at the end to the version you want. It will make the change for gcc and/or g++
ls -la /usr/bin/ | grep -oP "[S]*(gcc|g++)(-[a-z]+)*[s]" | xargs bash -c 'for link in ${@:1}; do sudo ln -s -f "/usr/bin/${link}-${0}" "/usr/bin/${link}"; done' 4.9
In this example I switched to 4.9
There are no error checks and what not in this example, so you might want to check what will be run before you run it. Just add echo before sudo. For completeness I provide check line as well:
ls -la /usr/bin/ | grep -oP "[S]*(gcc|g++)(-[a-z]+)*[s]" | xargs bash -c 'for link in ${@:1}; do echo sudo ln -s -f "/usr/bin/${link}-${0}" "/usr/bin/${link}"; done' 4.9
The output from the check should be something like:
sudo ln -s -f /usr/bin/g++-4.9 /usr/bin/g++
sudo ln -s -f /usr/bin/gcc-4.9 /usr/bin/gcc
sudo ln -s -f /usr/bin/gcc-ar-4.9 /usr/bin/gcc-ar
sudo ln -s -f /usr/bin/gcc-nm-4.9 /usr/bin/gcc-nm
sudo ln -s -f /usr/bin/gcc-ranlib-4.9 /usr/bin/gcc-ranlib
sudo ln -s -f /usr/bin/x86_64-linux-gnu-g++-4.9 /usr/bin/x86_64-linux-gnu-g++
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-4.9 /usr/bin/x86_64-linux-gnu-gcc
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-ar-4.9 /usr/bin/x86_64-linux-gnu-gcc-ar
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-nm-4.9 /usr/bin/x86_64-linux-gnu-gcc-nm
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-ranlib-4.9 /usr/bin/x86_64-linux-gnu-gcc-ranlib
You can check the version after with:
gcc --version
Semi-detailed explanation:
ls -la /usr/bin/ lists all files in /usr/bin
| pipe (send) the output to the next command
grep -oP matches the search regex per line. o only shows the result not the entire matched line. P tells grep to use perl-regex. I will not go into regex here, read up on it if you want to.
xargs simply put, it gathers the results that are piped to it and send all of them to the end. i.e. to the command following xargs
bash well, it's bash. The c flag tells it to use the string as a command. In this example it loops over the arguments sent from xargs by skipping the first (0th) argument, in this case the loop skips 4.9. The 0th argument is used in the loop to change the link.
ln -s -f The s flag makes a symbolic link, f forces unlinking first if needed.
2
Very old question, but this answer seems to be one of the gems we should look for when reviewing answers to old posts...
– mook765
Oct 16 '16 at 7:12
Brilliant! Best answer hands down!
– Gabriel Staples
Jan 15 '18 at 4:04
add a comment |
Edit:
This assumes that you have installed the version first, with e.g.:
sudo apt install gcc-4.9 g++-4.9
Original:
And here is a one-liner for those who are lazy, just change change the number at the end to the version you want. It will make the change for gcc and/or g++
ls -la /usr/bin/ | grep -oP "[S]*(gcc|g++)(-[a-z]+)*[s]" | xargs bash -c 'for link in ${@:1}; do sudo ln -s -f "/usr/bin/${link}-${0}" "/usr/bin/${link}"; done' 4.9
In this example I switched to 4.9
There are no error checks and what not in this example, so you might want to check what will be run before you run it. Just add echo before sudo. For completeness I provide check line as well:
ls -la /usr/bin/ | grep -oP "[S]*(gcc|g++)(-[a-z]+)*[s]" | xargs bash -c 'for link in ${@:1}; do echo sudo ln -s -f "/usr/bin/${link}-${0}" "/usr/bin/${link}"; done' 4.9
The output from the check should be something like:
sudo ln -s -f /usr/bin/g++-4.9 /usr/bin/g++
sudo ln -s -f /usr/bin/gcc-4.9 /usr/bin/gcc
sudo ln -s -f /usr/bin/gcc-ar-4.9 /usr/bin/gcc-ar
sudo ln -s -f /usr/bin/gcc-nm-4.9 /usr/bin/gcc-nm
sudo ln -s -f /usr/bin/gcc-ranlib-4.9 /usr/bin/gcc-ranlib
sudo ln -s -f /usr/bin/x86_64-linux-gnu-g++-4.9 /usr/bin/x86_64-linux-gnu-g++
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-4.9 /usr/bin/x86_64-linux-gnu-gcc
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-ar-4.9 /usr/bin/x86_64-linux-gnu-gcc-ar
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-nm-4.9 /usr/bin/x86_64-linux-gnu-gcc-nm
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-ranlib-4.9 /usr/bin/x86_64-linux-gnu-gcc-ranlib
You can check the version after with:
gcc --version
Semi-detailed explanation:
ls -la /usr/bin/ lists all files in /usr/bin
| pipe (send) the output to the next command
grep -oP matches the search regex per line. o only shows the result not the entire matched line. P tells grep to use perl-regex. I will not go into regex here, read up on it if you want to.
xargs simply put, it gathers the results that are piped to it and send all of them to the end. i.e. to the command following xargs
bash well, it's bash. The c flag tells it to use the string as a command. In this example it loops over the arguments sent from xargs by skipping the first (0th) argument, in this case the loop skips 4.9. The 0th argument is used in the loop to change the link.
ln -s -f The s flag makes a symbolic link, f forces unlinking first if needed.
2
Very old question, but this answer seems to be one of the gems we should look for when reviewing answers to old posts...
– mook765
Oct 16 '16 at 7:12
Brilliant! Best answer hands down!
– Gabriel Staples
Jan 15 '18 at 4:04
add a comment |
Edit:
This assumes that you have installed the version first, with e.g.:
sudo apt install gcc-4.9 g++-4.9
Original:
And here is a one-liner for those who are lazy, just change change the number at the end to the version you want. It will make the change for gcc and/or g++
ls -la /usr/bin/ | grep -oP "[S]*(gcc|g++)(-[a-z]+)*[s]" | xargs bash -c 'for link in ${@:1}; do sudo ln -s -f "/usr/bin/${link}-${0}" "/usr/bin/${link}"; done' 4.9
In this example I switched to 4.9
There are no error checks and what not in this example, so you might want to check what will be run before you run it. Just add echo before sudo. For completeness I provide check line as well:
ls -la /usr/bin/ | grep -oP "[S]*(gcc|g++)(-[a-z]+)*[s]" | xargs bash -c 'for link in ${@:1}; do echo sudo ln -s -f "/usr/bin/${link}-${0}" "/usr/bin/${link}"; done' 4.9
The output from the check should be something like:
sudo ln -s -f /usr/bin/g++-4.9 /usr/bin/g++
sudo ln -s -f /usr/bin/gcc-4.9 /usr/bin/gcc
sudo ln -s -f /usr/bin/gcc-ar-4.9 /usr/bin/gcc-ar
sudo ln -s -f /usr/bin/gcc-nm-4.9 /usr/bin/gcc-nm
sudo ln -s -f /usr/bin/gcc-ranlib-4.9 /usr/bin/gcc-ranlib
sudo ln -s -f /usr/bin/x86_64-linux-gnu-g++-4.9 /usr/bin/x86_64-linux-gnu-g++
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-4.9 /usr/bin/x86_64-linux-gnu-gcc
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-ar-4.9 /usr/bin/x86_64-linux-gnu-gcc-ar
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-nm-4.9 /usr/bin/x86_64-linux-gnu-gcc-nm
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-ranlib-4.9 /usr/bin/x86_64-linux-gnu-gcc-ranlib
You can check the version after with:
gcc --version
Semi-detailed explanation:
ls -la /usr/bin/ lists all files in /usr/bin
| pipe (send) the output to the next command
grep -oP matches the search regex per line. o only shows the result not the entire matched line. P tells grep to use perl-regex. I will not go into regex here, read up on it if you want to.
xargs simply put, it gathers the results that are piped to it and send all of them to the end. i.e. to the command following xargs
bash well, it's bash. The c flag tells it to use the string as a command. In this example it loops over the arguments sent from xargs by skipping the first (0th) argument, in this case the loop skips 4.9. The 0th argument is used in the loop to change the link.
ln -s -f The s flag makes a symbolic link, f forces unlinking first if needed.
Edit:
This assumes that you have installed the version first, with e.g.:
sudo apt install gcc-4.9 g++-4.9
Original:
And here is a one-liner for those who are lazy, just change change the number at the end to the version you want. It will make the change for gcc and/or g++
ls -la /usr/bin/ | grep -oP "[S]*(gcc|g++)(-[a-z]+)*[s]" | xargs bash -c 'for link in ${@:1}; do sudo ln -s -f "/usr/bin/${link}-${0}" "/usr/bin/${link}"; done' 4.9
In this example I switched to 4.9
There are no error checks and what not in this example, so you might want to check what will be run before you run it. Just add echo before sudo. For completeness I provide check line as well:
ls -la /usr/bin/ | grep -oP "[S]*(gcc|g++)(-[a-z]+)*[s]" | xargs bash -c 'for link in ${@:1}; do echo sudo ln -s -f "/usr/bin/${link}-${0}" "/usr/bin/${link}"; done' 4.9
The output from the check should be something like:
sudo ln -s -f /usr/bin/g++-4.9 /usr/bin/g++
sudo ln -s -f /usr/bin/gcc-4.9 /usr/bin/gcc
sudo ln -s -f /usr/bin/gcc-ar-4.9 /usr/bin/gcc-ar
sudo ln -s -f /usr/bin/gcc-nm-4.9 /usr/bin/gcc-nm
sudo ln -s -f /usr/bin/gcc-ranlib-4.9 /usr/bin/gcc-ranlib
sudo ln -s -f /usr/bin/x86_64-linux-gnu-g++-4.9 /usr/bin/x86_64-linux-gnu-g++
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-4.9 /usr/bin/x86_64-linux-gnu-gcc
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-ar-4.9 /usr/bin/x86_64-linux-gnu-gcc-ar
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-nm-4.9 /usr/bin/x86_64-linux-gnu-gcc-nm
sudo ln -s -f /usr/bin/x86_64-linux-gnu-gcc-ranlib-4.9 /usr/bin/x86_64-linux-gnu-gcc-ranlib
You can check the version after with:
gcc --version
Semi-detailed explanation:
ls -la /usr/bin/ lists all files in /usr/bin
| pipe (send) the output to the next command
grep -oP matches the search regex per line. o only shows the result not the entire matched line. P tells grep to use perl-regex. I will not go into regex here, read up on it if you want to.
xargs simply put, it gathers the results that are piped to it and send all of them to the end. i.e. to the command following xargs
bash well, it's bash. The c flag tells it to use the string as a command. In this example it loops over the arguments sent from xargs by skipping the first (0th) argument, in this case the loop skips 4.9. The 0th argument is used in the loop to change the link.
ln -s -f The s flag makes a symbolic link, f forces unlinking first if needed.
edited Feb 1 '17 at 12:50
answered Oct 15 '16 at 20:52
AleAle
14115
14115
2
Very old question, but this answer seems to be one of the gems we should look for when reviewing answers to old posts...
– mook765
Oct 16 '16 at 7:12
Brilliant! Best answer hands down!
– Gabriel Staples
Jan 15 '18 at 4:04
add a comment |
2
Very old question, but this answer seems to be one of the gems we should look for when reviewing answers to old posts...
– mook765
Oct 16 '16 at 7:12
Brilliant! Best answer hands down!
– Gabriel Staples
Jan 15 '18 at 4:04
2
2
Very old question, but this answer seems to be one of the gems we should look for when reviewing answers to old posts...
– mook765
Oct 16 '16 at 7:12
Very old question, but this answer seems to be one of the gems we should look for when reviewing answers to old posts...
– mook765
Oct 16 '16 at 7:12
Brilliant! Best answer hands down!
– Gabriel Staples
Jan 15 '18 at 4:04
Brilliant! Best answer hands down!
– Gabriel Staples
Jan 15 '18 at 4:04
add a comment |
Consider one way upgrade:
sudo apt install gcc-7
sudo apt remove gcc-5
apt will handle links staff automatically in this case. New C/C++ version is pretty compatible. You hardly would ever need old one.
1
This did not work on Ubuntu 18.04 and gcc-7 and gcc-8. After the removal of gcc-7 there is no link forgcc
.
– Werner Henze
Jan 11 at 11:03
@WernerHenze, in this case you also may need to reinstall g++ package which will update-alternatives for you.
– Sergei
Feb 15 at 11:40
add a comment |
Consider one way upgrade:
sudo apt install gcc-7
sudo apt remove gcc-5
apt will handle links staff automatically in this case. New C/C++ version is pretty compatible. You hardly would ever need old one.
1
This did not work on Ubuntu 18.04 and gcc-7 and gcc-8. After the removal of gcc-7 there is no link forgcc
.
– Werner Henze
Jan 11 at 11:03
@WernerHenze, in this case you also may need to reinstall g++ package which will update-alternatives for you.
– Sergei
Feb 15 at 11:40
add a comment |
Consider one way upgrade:
sudo apt install gcc-7
sudo apt remove gcc-5
apt will handle links staff automatically in this case. New C/C++ version is pretty compatible. You hardly would ever need old one.
Consider one way upgrade:
sudo apt install gcc-7
sudo apt remove gcc-5
apt will handle links staff automatically in this case. New C/C++ version is pretty compatible. You hardly would ever need old one.
edited Jan 28 '18 at 22:24
answered Oct 29 '17 at 20:02
SergeiSergei
20115
20115
1
This did not work on Ubuntu 18.04 and gcc-7 and gcc-8. After the removal of gcc-7 there is no link forgcc
.
– Werner Henze
Jan 11 at 11:03
@WernerHenze, in this case you also may need to reinstall g++ package which will update-alternatives for you.
– Sergei
Feb 15 at 11:40
add a comment |
1
This did not work on Ubuntu 18.04 and gcc-7 and gcc-8. After the removal of gcc-7 there is no link forgcc
.
– Werner Henze
Jan 11 at 11:03
@WernerHenze, in this case you also may need to reinstall g++ package which will update-alternatives for you.
– Sergei
Feb 15 at 11:40
1
1
This did not work on Ubuntu 18.04 and gcc-7 and gcc-8. After the removal of gcc-7 there is no link for
gcc
.– Werner Henze
Jan 11 at 11:03
This did not work on Ubuntu 18.04 and gcc-7 and gcc-8. After the removal of gcc-7 there is no link for
gcc
.– Werner Henze
Jan 11 at 11:03
@WernerHenze, in this case you also may need to reinstall g++ package which will update-alternatives for you.
– Sergei
Feb 15 at 11:40
@WernerHenze, in this case you also may need to reinstall g++ package which will update-alternatives for you.
– Sergei
Feb 15 at 11:40
add a comment |
How about a symbolic link in a temporary directory:
mkdir x && PATH=$PWD/x:$PATH && ln -s /usr/bin/g++-7 $PWD/x/g++
add a comment |
How about a symbolic link in a temporary directory:
mkdir x && PATH=$PWD/x:$PATH && ln -s /usr/bin/g++-7 $PWD/x/g++
add a comment |
How about a symbolic link in a temporary directory:
mkdir x && PATH=$PWD/x:$PATH && ln -s /usr/bin/g++-7 $PWD/x/g++
How about a symbolic link in a temporary directory:
mkdir x && PATH=$PWD/x:$PATH && ln -s /usr/bin/g++-7 $PWD/x/g++
answered Dec 5 '18 at 19:42
user643722user643722
11717
11717
add a comment |
add a comment |
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As @Oli explained, this is a bad idea. Debian-devel mail list: "I don't think alternatives should be used for versioning. For example, we don't use alternatives for gcc, neither for Python." lists.debian.org/debian-devel/2014/06/msg00381.html
– hmijail
Aug 18 '16 at 20:39
OK, so what do you use for versioning?
– WillC
Nov 28 '18 at 8:34