Bash: How to search the executables in path? - shell

I have a "gtags" executable in /usr/bin, but this is an older one.
Then I've compiled a new gtags and "make install" puts it in /usr/local/bin.
then I removed the one in /usr/bin. But when I typed "gtags" in shell, it told me that "/usr/bin/gtags" cannot found. But I have a "gtags" in /usr/local/bin, and the /usr/local/bin is in the PATH. Also, in my PATH, the /usr/local/bin is searched before /usr/bin, why the shell only checked "gtags" in /usr/bin?

Use the bash built-in command hash:
[root#localhost ~]# touch /bin/test.sh
[root#localhost ~]# chmod 755 /bin/test.sh
[root#localhost ~]# test.sh
[root#localhost ~]# mv /bin/test.sh /usr/local/bin/
[root#localhost ~]# test.sh
-bash: /bin/test.sh: No such file or directory
[root#localhost ~]# hash test.sh
[root#localhost ~]# test.sh
The reason this happens is bash "caches" where the binary is in $PATH so it doesn't have to find it each time it wants to run it. It's a performance thing. If you run "hash" with no arguments it'll report which commands its ran, how many times, and where it ran it from.

Related

Unable to modify /etc/shells on macOS to include brew installed version of bash

I am trying to update my /etc/shells file to include the path to a homebrew installed version of bash which resides at /usr/local/bin/bash
$ sudo echo /usr/local/bin/bash >> /etc/shells returns Permission denied and attempting to manually update is not allowed as it appears to be read-only.
Upon inspecting the file, the permissions are set as follows:
-rw-r--r-- 1 root wheel 179 Feb 21 2017 /etc/shells
So, with this in mind, and after looking at this article about Updating you shell with Homebrew I tried to initiate a shell as the root user and then try command above, i.e:
$ sudo -s
$ echo /usr/local/bin/bash >> /etc/shells
$ chsh -s /usr/local/bin/bash
However, this seems to hang on the first command ($ sudo -s). This spawns a bash process that eats up ~ 70% CPU and nothing happens.
Is there an alternative way one can update the /etc/shells/ file?
An approach to adding to a root-only file is echo /usr/local/bin/bash | sudo tee -a /etc/shells.
– Petesh
Would you be able to explain why that works and the sudo echo /usr/local/bin/bash >> /etc/shells does not though.
The latter doesn't work because the output redirection >> is (tried to be) applied by the shell before the sudo … is executed, and of course the user shell has no permission to do that.
Or you can just use this (I had to do this on macOS Mojave):
sudo sh -c "echo $(which zsh) >> /etc/shells"
chsh -s $(which zsh)

How to create symlinks in a specific directory

I'm working on an automated installation of a openSUSE system using AutoYAST, and I'm stumped on a small detail. In order to setup relevant applications in the user's environment, I try to symlink to all applications located in /usr/local/bin in ~/bin (so say /usr/local/bin has the addr2line utility, then I want to have a symlink to that in ~/bin).
I've tried to execute the following snipped to accomplish this:
su -c "for program in `ls /usr/local/bin`; do ln -s /usr/local/bin/$program ~/bin/$program; done" <user>
This snippet executes in the post-script phase of the automatic installation, which is executed as root (and seeing as I want the owner of the symlinks to be the user, this command is executed using su).
However, this does not work, and gives the following output:
++ ls /usr/local/bin
+ su -c 'for program in addr2line
ar
as
c++
c++filt
cpp
elfedit
g++
gcc
gcc-ar
gcc-nm
gcc-ranlib
gcov
gprof
i686-pc-linux-gnu-c++
i686-pc-linux-gnu-g++
i686-pc-linux-gnu-gcc
i686-pc-linux-gnu-gcc-4.9.3
i686-pc-linux-gnu-gcc-ar
i686-pc-linux-gnu-gcc-nm
i686-pc-linux-gnu-gcc-ranlib
ld
ld.bfd
nm
objcopy
objdump
ranlib
readelf
size
strings
strip; do ln -s /usr/local/bin/ ~/bin/; done' <user>
bash: -c: line 1: syntax error near unexpected token `ar'
bash: -c: line 1: `ar'
I've tried several variations of the command, but all seem to not exactly do what I want.
For example, I've also tried:
su -c "for program in /usr/local/bin/*; do ln -s $program ~/bin/; done" <user>
But this only created a symlink to /usr/local/bin in ~/bin.
So I'm a bit stuck on this one... Does anybody have an idea?
You're using double quotes to define your su command, so $program is being evaluated immediately. You want it evaluated when su executes the command. Use single quotes instead:
su -c 'for program in `ls /usr/local/bin`; do ln -s /usr/local/bin/$program ~/bin/$program; done' <user>
You can also use cp -s to create symlinks on a system with GNU cp (like your suse system), which gives you the ability to use recursion and the other fun options of cp.
In the end, I decided to go with the command posted by pacholik to fix this, as my original attempt was over-engineered and thus not necessary.
ln -s /usr/local/bin/* ~/bin

/usr/bin/env: ln: Too many levels of symbolic links

This problem is killing me and I feel like I've tried everything.
First off, the problem started happening when upgrading to Capistrano 3. Capistrano now utilizes /usr/bin/env before every command when deploying, to make sure the environment setup is correct.
When Capistrano goes to create symlinks to the necessary shared directory and respective files, it attempts commands like:
/usr/bin/env ln -s /full/path /different/full/path
...and then it errors out:
/usr/bin/env: ln: Too many levels of symbolic links
I realize it's not Capistrano's fault, so I began troubleshooting by ssh'ing to my server and trying the same command, and I receive the same error (which at least is good for consistency). I then try the same command without /usr/bin/env:
ln -s /full/path /different/full/path
And it works!!!! Maybe you can see the real solution that I can't?
here is the output of just the /usr/bin/env command:
rvm_bin_path=/home/deployer/.rvm/bin
GEM_HOME=/home/deployer/.rvm/gems/ruby-1.9.3-p392
TERM=xterm-256color
SHELL=/bin/bash
IRBRC=/home/deployer/.rvm/rubies/ruby-1.9.3-p392/.irbrc
SSH_CLIENT=...
OLDPWD=/home/deployer/Sites/example.com
MY_RUBY_HOME=/home/deployer/.rvm/rubies/ruby-1.9.3-p392
SSH_TTY=/dev/pts/0
USER=deployer
LS_COLORS= .....
_system_type=Linux
rvm_path=/home/deployer/.rvm
SSH_AUTH_SOCK=....
rvm_prefix=/home/deployer
MAIL=/var/mail/deployer
PATH=/home/deployer/.rvm/gems/ruby-1.9.3-p392/bin:/home/deployer/.rvm/gems/ruby-1.9.3-p392#global/bin:/home/deployer/.rvm/rubies/ruby-1.9.3-p392/bin:/home/deployer/.rvm/bin:/opt/rubyee/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/home/deployer/.rvm/bin
PWD=/home/deployer/Sites
LANG=en_US.UTF-8
_system_arch=i386
_system_version=12.04
rvm_version=1.26.4 (latest)
SHLVL=1
HOME=/home/deployer
LOGNAME=deployer
GEM_PATH=/home/deployer/.rvm/gems/ruby-1.9.3-p392:/home/deployer/.rvm/gems/ruby-1.9.3-p392#global
SSH_CONNECTION=....
LESSOPEN=| /usr/bin/lesspipe %s
LESSCLOSE=/usr/bin/lesspipe %s %s
RUBY_VERSION=ruby-1.9.3-p392
_system_name=Ubuntu
_=/usr/bin/env
I have also tried commands like the following, to find potential symlink loops:
find . -maxdepth 20 -type l -exec ls -ld {} +
But is not producing correct results:
lrwxrwxrwx 1 deployer deployer ...
You might not being using the same ln utility.
When invoking it directly from the interactive shell, ln might be overridden e.g. by an alias or by some shell function ln() {...;}.
This does not happen when /usr/bin/env tries to do that (AFAIK it looks for ln in PATH). I suspect that the ln it finds has issues, so you are getting this error.
This is an example scenario that might be similar to your case:
# start from an empty directory
$ ls -l
total 0
# create a problematic `ln` in the current directory
$ ln -s ln ln
$ ls -l
total 0
lrwxrwxrwx 1 me me 2 Jan 7 20:28 ln -> ln
# have an alias for the "real" ln
$ alias ln=/bin/ln
# mess up PATH
$ PATH="$PWD"
Now let's try the two alternatives, /usr/bin/env goes first:
$ /usr/bin/env ln -s /some/path /tmp/path
/usr/bin/env: ln: Too many levels of symbolic links
Then plain ln (remember that we aliased it):
$ ln -s /some/path /tmp/path
$ echo $?
0
$ /bin/ls -l /tmp/path
lrwxrwxrwx 1 me me 10 Jan 7 20:31 /tmp/path -> /some/path
So my suggestion is: look at issues with ln, e.g. by finding all different alternatives that might be visible. In bash you might run this:
$ type -a ln
Try this to find symlink loops:
find . -follow -printf ""
if you are using docker so you should install ruby in your case
docker run ruby
source
https://github.com/docker/for-win/issues/5763#issuecomment-585749243

Can't get shell script to run in Xcode

I'm fairly new to running scripts in Xcode and haven't been able to figure out whats wrong with the script I'm running. The first script I ran was this:
/bin/sh -x
PBXCP=${DEVELOPER_DIR}/Library/PrivateFrameworks/DevToolsCore.framework/Resources/pbxcp
${PBXCP} -exclude .svn "${PROJECT_DIR}/../../base"
"${BUILT_PRODUCTS_DIR}/${UNLOCALIZED_RESOURCES_FOLDER_PATH}/"
Which caused me to run into this error:
/Users/newperson/Library/Developer/Xcode/DerivedData/appname-etesgjzdmfzimlgvakidckjecgij
/Build
/Intermediates/appname.build/Debug-iphonesimulator/app.build/Script-
435F41A90F532CA300887552.sh: line 3: /Applications/Xcode.app/Contents/Developer/Library
/PrivateFrameworks/DevToolsCore.framework/Resources/pbxcp: No such file or directory
This error was fairly to the point, The file the script is looking for doesn't exist. The newer versions of Xcode have gotten rid of pbxcp. So I started looking for a good alternative script to run that wouldn't use pbxcp, when I found this:
/bin/sh -x
/usr/bin/tar -c -C "${PROJECT_DIR}/myframeworks" --exclude .DS_Store --exclude CVS --exclude
.svn --exclude .git -H `cd "${PROJECT_DIR}/myframeworks" && find DevToolsCore.framework` |
/usr/bin/tar -x -C ${BUILT_PRODUCTS_DIR}/${FRAMEWORKS_FOLDER_PATH}
This script also caused me to run into a problem, which was this:
tar: could not chdir to '/Users/newperson/Library/Developer/Xcode/DerivedData/appname-
etesgjzdmfzimlgvakidckjecgij/Build/Products/Debug-iphonesimulator/appname.app/Frameworks'
tar: Write error
Command /bin/sh failed with exit code 1
I couldn't find a clear answer to what this error meant, one forum suggest that I use the sudo command in my script to give the script permission to change directory, so I ran this:
/bin/sh -x
/usr/bin/tar -c -C "${PROJECT_DIR}/myframeworks" --exclude .DS_Store --exclude CVS --exclude
.svn --exclude .git -H `cd "${PROJECT_DIR}/myframeworks" && find DevToolsCore.framework`
| sudo /usr/bin/tar -x -C ${BUILT_PRODUCTS_DIR}/${FRAMEWORKS_FOLDER_PATH}
This script caused me to run into this error though:
tar: Write error
Command /bin/sh failed with exit code 1
++ find DevToolsCore.framework
sudo: no tty present and no askpass program specified
tar: Write error
This is as far as I got so far, I am fairly lost with my limited knowledge of shell script so any help correcting my script or finding a suitable replacement for the Xcode framework that contains pbxcp would be appreciated.
Change the permissions of the directory where your script wants to write files. Do it in an interactive session of Terminal:
$ sudo chmod a+w the_directory
Then you should be able to run your script (without sudoing the tar).

error when switching to directory: "perl version 5.12.3 can't run /usr/bin/shasum"

I installed rvm 1.9.3 and now whenever I switch to a directory containing a .rvmrc, I get a perl error message:
~/example$ cd .. && cd example
perl version 5.12.3 can't run /usr/bin/shasum. Try the alternative(s):
/usr/bin/shasum5.10.0 (uses perl 5.10.0)
Run "man perl" for more information about multiple version support in
Mac OS X.
You may try this dirty approach. This approach will skip those check and directly use shasum in your binary directory
$ cd /usr/bin
$ ls shasum*
shasum shasum5.10.0
$ mv /usr/bin/shasum /usr/bin/your_backup_shasum
$ ln -s shasum5.10.0 shasum

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