This question already has answers here:
How do I use sudo to redirect output to a location I don't have permission to write to? [closed]
(15 answers)
sudo cat << EOF > File doesn't work, sudo su does [duplicate]
(5 answers)
Closed 1 year ago.
I am trying to automate the addition of a repository source in my arch's pacman.conf file but using the echo command in my shell script. However, it fails like this:-
sudo echo "[archlinuxfr]" >> /etc/pacman.conf
sudo echo "Server = http://repo.archlinux.fr/\$arch" >> /etc/pacman.conf
sudo echo " " >> /etc/pacman.conf
-bash: /etc/pacman.conf: Permission denied
If I make changes to /etc/pacman.conf manually using vim, by doing
sudo vim /etc/pacman.conf
and quiting vim with :wq, everything works fine and my pacman.conf has been manually updated without "Permission denied" complaints.
Why is this so? And how do I get sudo echo to work? (btw, I tried using sudo cat too but that failed with Permission denied as well)
As #geekosaur explained, the shell does the redirection before running the command. When you type this:
sudo foo >/some/file
Your current shell process makes a copy of itself that first tries to open /some/file for writing, then if that succeeds it makes that file descriptor its standard output, and only if that succeeds does it execute sudo. This is failing at the first step.
If you're allowed (sudoer configs often preclude running shells), you can do something like this:
sudo bash -c 'foo >/some/file'
But I find a good solution in general is to use | sudo tee instead of > and | sudo tee -a instead of >>. That's especially useful if the redirection is the only reason I need sudo in the first place; after all, needlessly running processes as root is precisely what sudo was created to avoid. And running echo as root is just silly.
echo '[archlinuxfr]' | sudo tee -a /etc/pacman.conf >/dev/null
echo 'Server = http://repo.archlinux.fr/$arch' | sudo tee -a /etc/pacman.conf >/dev/null
echo ' ' | sudo tee -a /etc/pacman.conf >/dev/null
I added > /dev/null on the end because tee sends its output to both the named file and its own standard output, and I don't need to see it on my terminal. (The tee command acts like a "T" connector in a physical pipeline, which is where it gets its name.) And I switched to single quotes ('...') instead of doubles ("...") so that everything is literal and I didn't have to put a backslash in front of the $ in $arch. (Without the quotes or backslash, $arch would get replaced by the value of the shell parameter arch, which probably doesn't exist, in which case the $arch is replaced by nothing and just vanishes.)
So that takes care of writing to files as root using sudo. Now for a lengthy digression on ways to output newline-containing text in a shell script. :)
To BLUF it, as they say, my preferred solution would be to just feed a here-document into the above sudo tee command; then there is no need for cat or echo or printf or any other commands at all. The single quotation marks have moved to the sentinel introduction <<'EOF', but they have the same effect there: the body is treated as literal text, so $arch is left alone:
sudo tee -a /etc/pacman.conf >/dev/null <<'EOF'
[archlinuxfr]
Server = http://repo.archlinux.fr/$arch
EOF
But while that's how I'd do it, there are alternatives. Here are a few:
You can stick with one echo per line, but group all of them together in a subshell, so you only have to append to the file once:
(echo '[archlinuxfr]'
echo 'Server = http://repo.archlinux.fr/$arch'
echo ' ') | sudo tee -a /etc/pacman.conf >/dev/null
If you add -e to the echo (and you're using a shell that supports that non-POSIX extension), you can embed newlines directly into the string using \n:
# NON-POSIX - NOT RECOMMENDED
echo -e '[archlinuxfr]\nServer = http://repo.archlinux.fr/$arch\n ' |
sudo tee -a /etc/pacman.conf >/dev/null
But as it says above, that's not POSIX-specified behavior; your shell might just echo a literal -e followed by a string with a bunch of literal \ns instead. The POSIX way of doing that is to use printf instead of echo; it automatically treats its argument like echo -e does, but doesn't automatically append a newline at the end, so you have to stick an extra \n there, too:
printf '[archlinuxfr]\nServer = http://repo.archlinux.fr/$arch\n \n' |
sudo tee -a /etc/pacman.conf >/dev/null
With either of those solutions, what the command gets as an argument string contains the two-character sequence \n, and it's up to the command program itself (the code inside printf or echo) to translate that into a newline. In many modern shells, you have the option of using ANSI quotes $'...', which will translate sequences like \n into literal newlines before the command program ever sees the string. That means such strings work with any command whatsoever, including plain old -e-less echo:
echo $'[archlinuxfr]\nServer = http://repo.archlinux.fr/$arch\n ' |
sudo tee -a /etc/pacman.conf >/dev/null
But, while more portable than echo -e, ANSI quotes are still a non-POSIX extension.
And again, while those are all options, I prefer the straight tee <<EOF solution above.
The problem is that the redirection is being processed by your original shell, not by sudo. Shells are not capable of reading minds and do not know that that particular >> is meant for the sudo and not for it.
You need to:
quote the redirection ( so it is passed on to sudo)
and use sudo -s (so that sudo uses a shell to process the quoted redirection.)
http://www.innovationsts.com/blog/?p=2758
As the instructions are not that clear above I am using the instructions from that blog post. With examples so it is easier to see what you need to do.
$ sudo cat /root/example.txt | gzip > /root/example.gz
-bash: /root/example.gz: Permission denied
Notice that it’s the second command (the gzip command) in the pipeline that causes the error. That’s where our technique of using bash with the -c option comes in.
$ sudo bash -c 'cat /root/example.txt | gzip > /root/example.gz'
$ sudo ls /root/example.gz
/root/example.gz
We can see form the ls command’s output that the compressed file creation succeeded.
The second method is similar to the first in that we’re passing a command string to bash, but we’re doing it in a pipeline via sudo.
$ sudo rm /root/example.gz
$ echo "cat /root/example.txt | gzip > /root/example.gz" | sudo bash
$ sudo ls /root/example.gz
/root/example.gz
sudo bash -c 'echo "[archlinuxfr]" >> /etc/pacman.conf'
STEP 1 create a function in a bash file (write_pacman.sh)
#!/bin/bash
function write_pacman {
tee -a /etc/pacman.conf > /dev/null << 'EOF'
[archlinuxfr]
Server = http://repo.archlinux.fr/\$arch
EOF
}
'EOF' will not interpret $arch variable.
STE2 source bash file
$ source write_pacman.sh
STEP 3 execute function
$ write_pacman
append files (sudo cat):
cat <origin-file> | sudo tee -a <target-file>
append echo to file (sudo echo):
echo <origin> | sudo tee -a <target-file>
(EXTRA) disregard the ouput:
echo >origin> | sudo tee -a <target-file> >/dev/null
I'm working on something at the moment and just now I even wonder if what I am working on is even possible.
I want to SSH from jenkins to a shell script and use variables form a rc file that are in a git Repository. (The Shell script and rc file are in the same repo)
Nothing that I tried works and now I'm starting to wondering if it's even possible.
Here's is my local script but i get the same output on jenkins.
docker exec -it test-container bash 'sed -f <(printf "s/${DOMAIN}\.%s/www.&.${DOMAIN_SUFFIX_STAGE}/g\n" ${LANG_KEYS}) /var/www/foo/sed/test.txt > /var/www/foo/sed/new-2.txt'
No matter what I do I get this error
bash: sed -f <(printf "s/${DOMAIN}\.%s/www.&.${DOMAIN_SUFFIX_STAGE}/g\n" ${LANG_KEYS}) /var/www/foo/sed/test.txt > /var/www/foo/sed/new-2.txt: No such file or directory
And yes I can confirm that the directory is there
Here's an easier way to reproduce your problem:
$ bash "echo Hello"
bash: echo Hello: No such file or directory
This happens because the expected syntax is bash yourfile. The string you are passing is not a useful filename, so it fails.
To run a string argument as a command, you can use bash -c commandstring:
$ bash -c "echo Hello"
Hello
This makes bash interpret the parameter as a shell command to execute, instead of a filename to open.
I have a script that I'm trying to run but I just get the error ": command not found" whenever I try to run it. Here's what I've tried to do to fix it:
Made sure the hashbang is correct "#!/bin/bash"
Run dos2unix on the file
Run the script as scriptname.sh, ./scriptname.sh, and /bin/bash scriptname.sh
chmod 755 scriptname.sh
I still am unable to run the script. Any help is much appreciated!
This is caused by carriage returns. Here's the excerpt from the bash tag wiki:
Check whether your script or data has DOS style end-of-line characters
Use cat -v yourfile or echo "$yourvariable" | cat -v .
DOS carriage returns will show up as ^M after each line.
If you find them, delete them using dos2unix (a.k.a. fromdos) or tr -d '\r'
Make sure to check all your data, and not just the script itself.
You can use these to delete unnecessary characters:
tr -cd '[:alnum:][:blank:][:punct:]\n' < script.sh > new_script.sh
Or
tr -cd '[:graph:][:blank:]\n' < script.sh > new_script.sh
Then try new_script.sh.
I have a script that I'm trying to run but I just get the error ": command not found" whenever I try to run it. Here's what I've tried to do to fix it:
Made sure the hashbang is correct "#!/bin/bash"
Run dos2unix on the file
Run the script as scriptname.sh, ./scriptname.sh, and /bin/bash scriptname.sh
chmod 755 scriptname.sh
I still am unable to run the script. Any help is much appreciated!
This is caused by carriage returns. Here's the excerpt from the bash tag wiki:
Check whether your script or data has DOS style end-of-line characters
Use cat -v yourfile or echo "$yourvariable" | cat -v .
DOS carriage returns will show up as ^M after each line.
If you find them, delete them using dos2unix (a.k.a. fromdos) or tr -d '\r'
Make sure to check all your data, and not just the script itself.
You can use these to delete unnecessary characters:
tr -cd '[:alnum:][:blank:][:punct:]\n' < script.sh > new_script.sh
Or
tr -cd '[:graph:][:blank:]\n' < script.sh > new_script.sh
Then try new_script.sh.
Looking over the Dokku source code, I noticed two uses of pipe and redirect that I am not familiar with.
One is: cat | command
Example: id=$(cat | docker run -i -a stdin progrium/buildstep /bin/bash -c "mkdir -p /app && tar -xC /app")
The other is cat > file
Example: id=$(cat "$HOME/$APP/ENV" | docker run -i -a stdin $IMAGE /bin/bash -c "mkdir -p /app/.profile.d && cat > /app/.profile.d/app-env.sh")
What is the use of pipe and redirect in the two cases?
Normally, both usages are completely useless.
cat without arguments reads from stdin, and writes to stdout.
cat | command is equivalent with command.
&& cat >file is equivalent with >file, assuming the previous command processed the stdin input.
Looking at it more closely, the sole purpose of that cat command in the second example is to read from stdin. Without it, you would redirect the output of mkdir to the file. So the command first makes sure the directory exists, then writes to the file whatever you feed to it through the stdin.