Expand variables in local bash script before passing it to SSH
I am trying to execute a script on a remote host through SSH. The script uses environment variables that are set on the local shell. The variables in the script are not expanded.
ssh user@host 'bash -s' < script.sh
Contents of script.sh:
#!/bin/bash
docker pull "$IMAGE"
On the remote host this is executed as:
docker pull ""
As indicated by the error output:
Error parsing reference: "" is not a valid repository/tag: repository name must have at least one component
I've tried to use command substitution:
ssh user@host < $(cat script.sh)
Which leads to:
bash: line 95: $(cat script.sh): ambiguous redirect
How can I make the variables in script.sh expand before passing the commands over SSH?
bash ssh environment-variables
edited 5 hours ago
Jeff Schaller
39.7k1054126
asked 5 hours ago
ThomasThomas
31
New contributor
Thomas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
|
show 1 more comment
I am trying to execute a script on a remote host through SSH. The script uses environment variables that are set on the local shell. The variables in the script are not expanded.
ssh user@host 'bash -s' < script.sh
Contents of script.sh:
#!/bin/bash
docker pull "$IMAGE"
On the remote host this is executed as:
docker pull ""
As indicated by the error output:
Error parsing reference: "" is not a valid repository/tag: repository name must have at least one component
I've tried to use command substitution:
ssh user@host < $(cat script.sh)
Which leads to:
bash: line 95: $(cat script.sh): ambiguous redirect
How can I make the variables in script.sh expand before passing the commands over SSH?
bash ssh environment-variables
edited 5 hours ago
Jeff Schaller
39.7k1054126
asked 5 hours ago
ThomasThomas
31
New contributor
Thomas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
1
Do you just need $IMAGE, or are there others that aren't apparent?
– Jeff Schaller
5 hours ago
There are others as well
– Thomas
5 hours ago
Are you able to enumerate them, or do you prefer to send every environmental variable over?
– Jeff Schaller
5 hours ago
The environment variables must all remain local, I'm not entirely sure what you mean by enumerating them in this context
– Thomas
5 hours ago
If there's just IMAGE, FOO, and BAR, that's one case; if there are dozens of others, that's the other case.
– Jeff Schaller
5 hours ago
|
show 1 more comment
I am trying to execute a script on a remote host through SSH. The script uses environment variables that are set on the local shell. The variables in the script are not expanded.
ssh user@host 'bash -s' < script.sh
Contents of script.sh:
#!/bin/bash
docker pull "$IMAGE"
On the remote host this is executed as:
docker pull ""
As indicated by the error output:
Error parsing reference: "" is not a valid repository/tag: repository name must have at least one component
I've tried to use command substitution:
ssh user@host < $(cat script.sh)
Which leads to:
bash: line 95: $(cat script.sh): ambiguous redirect
How can I make the variables in script.sh expand before passing the commands over SSH?
bash ssh environment-variables
edited 5 hours ago
Jeff Schaller
39.7k1054126
asked 5 hours ago
ThomasThomas
31
New contributor
Thomas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I am trying to execute a script on a remote host through SSH. The script uses environment variables that are set on the local shell. The variables in the script are not expanded.
ssh user@host 'bash -s' < script.sh
Contents of script.sh:
#!/bin/bash
docker pull "$IMAGE"
On the remote host this is executed as:
docker pull ""
As indicated by the error output:
Error parsing reference: "" is not a valid repository/tag: repository name must have at least one component
I've tried to use command substitution:
ssh user@host < $(cat script.sh)
Which leads to:
bash: line 95: $(cat script.sh): ambiguous redirect
How can I make the variables in script.sh expand before passing the commands over SSH?
bash ssh environment-variables
bash ssh environment-variables
edited 5 hours ago
Jeff Schaller
39.7k1054126
asked 5 hours ago
ThomasThomas
31
New contributor
Thomas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 5 hours ago
Jeff Schaller
39.7k1054126
asked 5 hours ago
ThomasThomas
31
New contributor
Thomas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 5 hours ago
Jeff Schaller
39.7k1054126
edited 5 hours ago
Jeff Schaller
39.7k1054126
edited 5 hours ago
Jeff Schaller
39.7k1054126
39.7k1054126
asked 5 hours ago
ThomasThomas
31
New contributor
Thomas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 5 hours ago
ThomasThomas
31
asked 5 hours ago
ThomasThomas
31
31
New contributor
Thomas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Thomas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Thomas is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
1
Do you just need $IMAGE, or are there others that aren't apparent?
– Jeff Schaller
5 hours ago
There are others as well
– Thomas
5 hours ago
Are you able to enumerate them, or do you prefer to send every environmental variable over?
– Jeff Schaller
5 hours ago
The environment variables must all remain local, I'm not entirely sure what you mean by enumerating them in this context
– Thomas
5 hours ago
If there's just IMAGE, FOO, and BAR, that's one case; if there are dozens of others, that's the other case.
– Jeff Schaller
5 hours ago
|
show 1 more comment
1
Do you just need $IMAGE, or are there others that aren't apparent?
– Jeff Schaller
5 hours ago
There are others as well
– Thomas
5 hours ago
Are you able to enumerate them, or do you prefer to send every environmental variable over?
– Jeff Schaller
5 hours ago
The environment variables must all remain local, I'm not entirely sure what you mean by enumerating them in this context
– Thomas
5 hours ago
If there's just IMAGE, FOO, and BAR, that's one case; if there are dozens of others, that's the other case.
– Jeff Schaller
5 hours ago
1
1
Do you just need $IMAGE, or are there others that aren't apparent?
– Jeff Schaller
5 hours ago
Do you just need $IMAGE, or are there others that aren't apparent?
– Jeff Schaller
5 hours ago
There are others as well
– Thomas
5 hours ago
There are others as well
– Thomas
5 hours ago
Are you able to enumerate them, or do you prefer to send every environmental variable over?
– Jeff Schaller
5 hours ago
Are you able to enumerate them, or do you prefer to send every environmental variable over?
– Jeff Schaller
5 hours ago
The environment variables must all remain local, I'm not entirely sure what you mean by enumerating them in this context
– Thomas
5 hours ago
The environment variables must all remain local, I'm not entirely sure what you mean by enumerating them in this context
– Thomas
5 hours ago
If there's just IMAGE, FOO, and BAR, that's one case; if there are dozens of others, that's the other case.
– Jeff Schaller
5 hours ago
If there's just IMAGE, FOO, and BAR, that's one case; if there are dozens of others, that's the other case.
– Jeff Schaller
5 hours ago
|
show 1 more comment
1 Answer
1
active
oldest
votes
You can in principle send environment variables to the remote over SSH, but at least OpenSSH disallows it on the server, and doesn't try to send any from the client. The relevant configuration options are AcceptEnv in sshd_config (server) and SendEnv in ssh_config (client).
Assuming you can't or don't want to change the configuration there, since you're sending a whole script to the stdin on the remote anyway, you could also stick the variable assignments in front of that script.
We can use export -p to print out all the exported variables in the current shell, in a format that the remote shell can use to assign them there. Then the remote can process the script as usual, with the variables set.
So with script.sh containing
echo "$FOO" "$HOSTNAME"
This would export FOO in the local shell, and then pass the definitions of all exported variables to remote, along with the script itself. The resulting output contains the value of FOO that was just set.
$ export FOO=abc123
$ (export -p; cat script.sh) | ssh user@remotehost 'bash -s'
FOO: abc123 HOSTNAME: remotehost
(There's a slight problem with Bash here. In normal mode, its export -p prints out declare commands instead of the standard export, and those may not be supported by other shells. So if your local shell is Bash, and you'd start a standard sh on the remote, you'd get errors.)
answered 4 hours ago
ilkkachuilkkachu
56.9k785158
Thank you for the explanation, however, my intention is not to send the env vars to the remote host, they should remain local. What I am trying to send to the remote host are the commands fromscript.shwith the vars already expanded. Your second suggestion seems interesting, could we shape that in a way to achieve the aformentioned goal? (I already tried command substitution, but without invokingbash, would that make a difference?)
– Thomas
4 hours ago
@Thomas, mhh, does it matter which way you do it? If I didn't get this too wrong, thatdocker pull "$IMAGE"should work just as if with the local value ofIMAGEif the export definitions are pushed to the remote. Pre-expanding the variables within the script text would be really problematic in the general case. Any quotes and other shell syntax characters within the values would take effect during parsing, which they don't if the variables are kept just as variables.
– ilkkachu
4 hours ago
Sorry, I misunderstood the concept. I've been experimenting with your solution and it seems to do exactly what I want, thank you (process subtitution is a new one to me). Guess the frustration of the past several hours got to me, haha. Marked as best answer -- thanks again!
– Thomas
3 hours ago
@Thomas, ah ok, good. I'm sorry I wasn't able to explain the idea better. Process substitution isn't really the point, mentioning it might just have been confusing here. It's mostly like a generalized replacement for pipes (see mywiki.wooledge.org/ProcessSubstitution or related questions here). Neither that or command substitution do anything about the contents of the files. I think the names refer to the fact that e.g.$(somecmd)is itself substituted on the command line with the output of `somecmd.
– ilkkachu
3 hours ago
add a comment |
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You can in principle send environment variables to the remote over SSH, but at least OpenSSH disallows it on the server, and doesn't try to send any from the client. The relevant configuration options are AcceptEnv in sshd_config (server) and SendEnv in ssh_config (client).
Assuming you can't or don't want to change the configuration there, since you're sending a whole script to the stdin on the remote anyway, you could also stick the variable assignments in front of that script.
We can use export -p to print out all the exported variables in the current shell, in a format that the remote shell can use to assign them there. Then the remote can process the script as usual, with the variables set.
So with script.sh containing
echo "$FOO" "$HOSTNAME"
This would export FOO in the local shell, and then pass the definitions of all exported variables to remote, along with the script itself. The resulting output contains the value of FOO that was just set.
$ export FOO=abc123
$ (export -p; cat script.sh) | ssh user@remotehost 'bash -s'
FOO: abc123 HOSTNAME: remotehost
(There's a slight problem with Bash here. In normal mode, its export -p prints out declare commands instead of the standard export, and those may not be supported by other shells. So if your local shell is Bash, and you'd start a standard sh on the remote, you'd get errors.)
answered 4 hours ago
ilkkachuilkkachu
56.9k785158
Thank you for the explanation, however, my intention is not to send the env vars to the remote host, they should remain local. What I am trying to send to the remote host are the commands fromscript.shwith the vars already expanded. Your second suggestion seems interesting, could we shape that in a way to achieve the aformentioned goal? (I already tried command substitution, but without invokingbash, would that make a difference?)
– Thomas
4 hours ago
@Thomas, mhh, does it matter which way you do it? If I didn't get this too wrong, thatdocker pull "$IMAGE"should work just as if with the local value ofIMAGEif the export definitions are pushed to the remote. Pre-expanding the variables within the script text would be really problematic in the general case. Any quotes and other shell syntax characters within the values would take effect during parsing, which they don't if the variables are kept just as variables.
– ilkkachu
4 hours ago
Sorry, I misunderstood the concept. I've been experimenting with your solution and it seems to do exactly what I want, thank you (process subtitution is a new one to me). Guess the frustration of the past several hours got to me, haha. Marked as best answer -- thanks again!
– Thomas
3 hours ago
@Thomas, ah ok, good. I'm sorry I wasn't able to explain the idea better. Process substitution isn't really the point, mentioning it might just have been confusing here. It's mostly like a generalized replacement for pipes (see mywiki.wooledge.org/ProcessSubstitution or related questions here). Neither that or command substitution do anything about the contents of the files. I think the names refer to the fact that e.g.$(somecmd)is itself substituted on the command line with the output of `somecmd.
– ilkkachu
3 hours ago
add a comment |
You can in principle send environment variables to the remote over SSH, but at least OpenSSH disallows it on the server, and doesn't try to send any from the client. The relevant configuration options are AcceptEnv in sshd_config (server) and SendEnv in ssh_config (client).
Assuming you can't or don't want to change the configuration there, since you're sending a whole script to the stdin on the remote anyway, you could also stick the variable assignments in front of that script.
We can use export -p to print out all the exported variables in the current shell, in a format that the remote shell can use to assign them there. Then the remote can process the script as usual, with the variables set.
So with script.sh containing
echo "$FOO" "$HOSTNAME"
This would export FOO in the local shell, and then pass the definitions of all exported variables to remote, along with the script itself. The resulting output contains the value of FOO that was just set.
$ export FOO=abc123
$ (export -p; cat script.sh) | ssh user@remotehost 'bash -s'
FOO: abc123 HOSTNAME: remotehost
(There's a slight problem with Bash here. In normal mode, its export -p prints out declare commands instead of the standard export, and those may not be supported by other shells. So if your local shell is Bash, and you'd start a standard sh on the remote, you'd get errors.)
answered 4 hours ago
ilkkachuilkkachu
56.9k785158
Thank you for the explanation, however, my intention is not to send the env vars to the remote host, they should remain local. What I am trying to send to the remote host are the commands fromscript.shwith the vars already expanded. Your second suggestion seems interesting, could we shape that in a way to achieve the aformentioned goal? (I already tried command substitution, but without invokingbash, would that make a difference?)
– Thomas
4 hours ago
@Thomas, mhh, does it matter which way you do it? If I didn't get this too wrong, thatdocker pull "$IMAGE"should work just as if with the local value ofIMAGEif the export definitions are pushed to the remote. Pre-expanding the variables within the script text would be really problematic in the general case. Any quotes and other shell syntax characters within the values would take effect during parsing, which they don't if the variables are kept just as variables.
– ilkkachu
4 hours ago
Sorry, I misunderstood the concept. I've been experimenting with your solution and it seems to do exactly what I want, thank you (process subtitution is a new one to me). Guess the frustration of the past several hours got to me, haha. Marked as best answer -- thanks again!
– Thomas
3 hours ago
@Thomas, ah ok, good. I'm sorry I wasn't able to explain the idea better. Process substitution isn't really the point, mentioning it might just have been confusing here. It's mostly like a generalized replacement for pipes (see mywiki.wooledge.org/ProcessSubstitution or related questions here). Neither that or command substitution do anything about the contents of the files. I think the names refer to the fact that e.g.$(somecmd)is itself substituted on the command line with the output of `somecmd.
– ilkkachu
3 hours ago
add a comment |
You can in principle send environment variables to the remote over SSH, but at least OpenSSH disallows it on the server, and doesn't try to send any from the client. The relevant configuration options are AcceptEnv in sshd_config (server) and SendEnv in ssh_config (client).
Assuming you can't or don't want to change the configuration there, since you're sending a whole script to the stdin on the remote anyway, you could also stick the variable assignments in front of that script.
We can use export -p to print out all the exported variables in the current shell, in a format that the remote shell can use to assign them there. Then the remote can process the script as usual, with the variables set.
So with script.sh containing
echo "$FOO" "$HOSTNAME"
This would export FOO in the local shell, and then pass the definitions of all exported variables to remote, along with the script itself. The resulting output contains the value of FOO that was just set.
$ export FOO=abc123
$ (export -p; cat script.sh) | ssh user@remotehost 'bash -s'
FOO: abc123 HOSTNAME: remotehost
(There's a slight problem with Bash here. In normal mode, its export -p prints out declare commands instead of the standard export, and those may not be supported by other shells. So if your local shell is Bash, and you'd start a standard sh on the remote, you'd get errors.)
answered 4 hours ago
ilkkachuilkkachu
56.9k785158
You can in principle send environment variables to the remote over SSH, but at least OpenSSH disallows it on the server, and doesn't try to send any from the client. The relevant configuration options are AcceptEnv in sshd_config (server) and SendEnv in ssh_config (client).
Assuming you can't or don't want to change the configuration there, since you're sending a whole script to the stdin on the remote anyway, you could also stick the variable assignments in front of that script.
We can use export -p to print out all the exported variables in the current shell, in a format that the remote shell can use to assign them there. Then the remote can process the script as usual, with the variables set.
So with script.sh containing
echo "$FOO" "$HOSTNAME"
This would export FOO in the local shell, and then pass the definitions of all exported variables to remote, along with the script itself. The resulting output contains the value of FOO that was just set.
$ export FOO=abc123
$ (export -p; cat script.sh) | ssh user@remotehost 'bash -s'
FOO: abc123 HOSTNAME: remotehost
(There's a slight problem with Bash here. In normal mode, its export -p prints out declare commands instead of the standard export, and those may not be supported by other shells. So if your local shell is Bash, and you'd start a standard sh on the remote, you'd get errors.)
answered 4 hours ago
ilkkachuilkkachu
56.9k785158
edited 3 hours ago
answered 4 hours ago
ilkkachuilkkachu
56.9k785158
answered 4 hours ago
ilkkachuilkkachu
56.9k785158
answered 4 hours ago
ilkkachuilkkachu
56.9k785158
56.9k785158
Thank you for the explanation, however, my intention is not to send the env vars to the remote host, they should remain local. What I am trying to send to the remote host are the commands fromscript.shwith the vars already expanded. Your second suggestion seems interesting, could we shape that in a way to achieve the aformentioned goal? (I already tried command substitution, but without invokingbash, would that make a difference?)
– Thomas
4 hours ago
@Thomas, mhh, does it matter which way you do it? If I didn't get this too wrong, thatdocker pull "$IMAGE"should work just as if with the local value ofIMAGEif the export definitions are pushed to the remote. Pre-expanding the variables within the script text would be really problematic in the general case. Any quotes and other shell syntax characters within the values would take effect during parsing, which they don't if the variables are kept just as variables.
– ilkkachu
4 hours ago
Sorry, I misunderstood the concept. I've been experimenting with your solution and it seems to do exactly what I want, thank you (process subtitution is a new one to me). Guess the frustration of the past several hours got to me, haha. Marked as best answer -- thanks again!
– Thomas
3 hours ago
@Thomas, ah ok, good. I'm sorry I wasn't able to explain the idea better. Process substitution isn't really the point, mentioning it might just have been confusing here. It's mostly like a generalized replacement for pipes (see mywiki.wooledge.org/ProcessSubstitution or related questions here). Neither that or command substitution do anything about the contents of the files. I think the names refer to the fact that e.g.$(somecmd)is itself substituted on the command line with the output of `somecmd.
– ilkkachu
3 hours ago
add a comment |
Thank you for the explanation, however, my intention is not to send the env vars to the remote host, they should remain local. What I am trying to send to the remote host are the commands fromscript.shwith the vars already expanded. Your second suggestion seems interesting, could we shape that in a way to achieve the aformentioned goal? (I already tried command substitution, but without invokingbash, would that make a difference?)
– Thomas
4 hours ago
@Thomas, mhh, does it matter which way you do it? If I didn't get this too wrong, thatdocker pull "$IMAGE"should work just as if with the local value ofIMAGEif the export definitions are pushed to the remote. Pre-expanding the variables within the script text would be really problematic in the general case. Any quotes and other shell syntax characters within the values would take effect during parsing, which they don't if the variables are kept just as variables.
– ilkkachu
4 hours ago
Sorry, I misunderstood the concept. I've been experimenting with your solution and it seems to do exactly what I want, thank you (process subtitution is a new one to me). Guess the frustration of the past several hours got to me, haha. Marked as best answer -- thanks again!
– Thomas
3 hours ago
@Thomas, ah ok, good. I'm sorry I wasn't able to explain the idea better. Process substitution isn't really the point, mentioning it might just have been confusing here. It's mostly like a generalized replacement for pipes (see mywiki.wooledge.org/ProcessSubstitution or related questions here). Neither that or command substitution do anything about the contents of the files. I think the names refer to the fact that e.g.$(somecmd)is itself substituted on the command line with the output of `somecmd.
– ilkkachu
3 hours ago
Thank you for the explanation, however, my intention is not to send the env vars to the remote host, they should remain local. What I am trying to send to the remote host are the commands from
script.shwith the vars already expanded. Your second suggestion seems interesting, could we shape that in a way to achieve the aformentioned goal? (I already tried command substitution, but without invoking bash, would that make a difference?)– Thomas
4 hours ago
Thank you for the explanation, however, my intention is not to send the env vars to the remote host, they should remain local. What I am trying to send to the remote host are the commands from
script.shwith the vars already expanded. Your second suggestion seems interesting, could we shape that in a way to achieve the aformentioned goal? (I already tried command substitution, but without invoking bash, would that make a difference?)– Thomas
4 hours ago
@Thomas, mhh, does it matter which way you do it? If I didn't get this too wrong, that
docker pull "$IMAGE" should work just as if with the local value of IMAGE if the export definitions are pushed to the remote. Pre-expanding the variables within the script text would be really problematic in the general case. Any quotes and other shell syntax characters within the values would take effect during parsing, which they don't if the variables are kept just as variables.– ilkkachu
4 hours ago
@Thomas, mhh, does it matter which way you do it? If I didn't get this too wrong, that
docker pull "$IMAGE" should work just as if with the local value of IMAGE if the export definitions are pushed to the remote. Pre-expanding the variables within the script text would be really problematic in the general case. Any quotes and other shell syntax characters within the values would take effect during parsing, which they don't if the variables are kept just as variables.– ilkkachu
4 hours ago
Sorry, I misunderstood the concept. I've been experimenting with your solution and it seems to do exactly what I want, thank you (process subtitution is a new one to me). Guess the frustration of the past several hours got to me, haha. Marked as best answer -- thanks again!
– Thomas
3 hours ago
Sorry, I misunderstood the concept. I've been experimenting with your solution and it seems to do exactly what I want, thank you (process subtitution is a new one to me). Guess the frustration of the past several hours got to me, haha. Marked as best answer -- thanks again!
– Thomas
3 hours ago
@Thomas, ah ok, good. I'm sorry I wasn't able to explain the idea better. Process substitution isn't really the point, mentioning it might just have been confusing here. It's mostly like a generalized replacement for pipes (see mywiki.wooledge.org/ProcessSubstitution or related questions here). Neither that or command substitution do anything about the contents of the files. I think the names refer to the fact that e.g.
$(somecmd) is itself substituted on the command line with the output of `somecmd.– ilkkachu
3 hours ago
@Thomas, ah ok, good. I'm sorry I wasn't able to explain the idea better. Process substitution isn't really the point, mentioning it might just have been confusing here. It's mostly like a generalized replacement for pipes (see mywiki.wooledge.org/ProcessSubstitution or related questions here). Neither that or command substitution do anything about the contents of the files. I think the names refer to the fact that e.g.
$(somecmd) is itself substituted on the command line with the output of `somecmd.– ilkkachu
3 hours ago
add a comment |
Thomas is a new contributor. Be nice, and check out our Code of Conduct.
Thomas is a new contributor. Be nice, and check out our Code of Conduct.
Thomas is a new contributor. Be nice, and check out our Code of Conduct.
Thomas is a new contributor. Be nice, and check out our Code of Conduct.
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1
Do you just need $IMAGE, or are there others that aren't apparent?
– Jeff Schaller
5 hours ago
There are others as well
– Thomas
5 hours ago
Are you able to enumerate them, or do you prefer to send every environmental variable over?
– Jeff Schaller
5 hours ago
The environment variables must all remain local, I'm not entirely sure what you mean by enumerating them in this context
– Thomas
5 hours ago
If there's just IMAGE, FOO, and BAR, that's one case; if there are dozens of others, that's the other case.
– Jeff Schaller
5 hours ago