configuring fish shell prompt inside nix-shell - shell

I tried following the steps here to configure the prompt: https://nixos.wiki/wiki/Fish
Combined with the information here about the location and content of a basic file: https://fishshell.com/docs/current/faq.html#how-do-i-set-my-prompt
If I understood correctly the content of fish_prompt.fish should be:
set -l nix_shell_info (
if test -n "$IN_NIX_SHELL"
echo -n "<nix-shell> "
end
)
function fish_prompt
set_color $fish_color_cwd
echo -n (prompt_pwd)
set_color normal
echo -n -s ' $nix_shell_info ~>'
end
After setting it this way the prompt is the same whether in a nix-shell or not and the variable $nix_shell_info does not get set.
How can I set it so that it works as intended?

You need to set the variable inside the function, otherwise it would always contain the value set when the file was loaded:
function fish_prompt
set -l nix_shell_info (
if test -n "$IN_NIX_SHELL"
echo -n "<nix-shell> "
end
)
set_color $fish_color_cwd
echo -n (prompt_pwd)
set_color normal
echo -n -s " $nix_shell_info ~>"
end
Edit: As cole-h pointed out on IRC, you also need to also change the single quotes containing the variable to double quotes or it will not be interpolated.

Related

How to set AND expand variables in a heredoc section

I have a heredoc that needs to call existing variables from the main script, and set its own variables to use later. Something like this:
count=0
ssh $other_host <<ENDSSH
if [[ "${count}" == "0" ]]; then
output="string1"
else
output="string2"
fi
echo output
ENDSSH
That doesn't work because 'output' doesn't get set to anything.
I tried using the solution from this question:
count=0
ssh $other_host << \ENDSSH
if [[ "${count}" == "0" ]]; then
output="string1"
else
output="string2"
fi
echo output
ENDSSH
It didn't work either. $output got set to "string2" because $count wasn't expanded.
How can I use a heredoc that expands variables from the parent script, and sets its own variables?
You can use:
count=0
ssh -t -t "$other_host" << ENDSSH
if [[ "${count}" == "0" ]]; then
output="string1"
else
output="string2"
fi
echo "\$output"
exit
ENDSSH
We use \$output so that it is expanded on remote host not locally.
It is better not to use stdin (such as by using here-docs) to pass commands to ssh.
If you use a command-line argument to pass your shell commands instead, you can better separate what is expanded locally and what will be executed remotely:
# Use a *literal* here-doc to read the script into a *variable*.
# Note how the script references parameter $1 instead of
# local variable $count.
read -d '' -r script <<'EOF'
[[ $1 == '0' ]] && output='zero' || output='nonzero'
echo "$output"
EOF
# The variable whose value to pass as a parameter.
# With value 0, the script will echo 'zero', otherwise 'nonzero'.
count=0
# Use `set -- '$<local-var>'...;` to pass the local variables as
# positional parameters, followed by the script code.
ssh localhost "set -- '$count'; $script"
You can escape the variables as #anubhava said, or, if you get too much variables for the escaping, you can do it in two steps:
# prepare the part which should not be expanded
# note the quoted 'EOF'
read -r -d '' commands <<'EOF'
if [[ "$count" == "0" ]]; then
echo "$count - $HOME"
else
echo "$count - $PATH"
fi
EOF
localcount=1
#use the unquoted ENDSSH
ssh me#nox.local <<ENDSSH
count=$localcount # count=1
#here will be inserted the above prepared commands
$commands
ENDSSH
will print something like:
1 - /usr/bin:/bin:/usr/sbin:/sbin

Variable scope in Bash [duplicate]

Please explain to me why the very last echo statement is blank? I expect that XCODE is incremented in the while loop to a value of 1:
#!/bin/bash
OUTPUT="name1 ip ip status" # normally output of another command with multi line output
if [ -z "$OUTPUT" ]
then
echo "Status WARN: No messages from SMcli"
exit $STATE_WARNING
else
echo "$OUTPUT"|while read NAME IP1 IP2 STATUS
do
if [ "$STATUS" != "Optimal" ]
then
echo "CRIT: $NAME - $STATUS"
echo $((++XCODE))
else
echo "OK: $NAME - $STATUS"
fi
done
fi
echo $XCODE
I've tried using the following statement instead of the ++XCODE method
XCODE=`expr $XCODE + 1`
and it too won't print outside of the while statement. I think I'm missing something about variable scope here, but the ol' man page isn't showing it to me.
Because you're piping into the while loop, a sub-shell is created to run the while loop.
Now this child process has its own copy of the environment and can't pass any
variables back to its parent (as in any unix process).
Therefore you'll need to restructure so that you're not piping into the loop.
Alternatively you could run in a function, for example, and echo the value you
want returned from the sub-process.
http://tldp.org/LDP/abs/html/subshells.html#SUBSHELL
The problem is that processes put together with a pipe are executed in subshells (and therefore have their own environment). Whatever happens within the while does not affect anything outside of the pipe.
Your specific example can be solved by rewriting the pipe to
while ... do ... done <<< "$OUTPUT"
or perhaps
while ... do ... done < <(echo "$OUTPUT")
This should work as well (because echo and while are in same subshell):
#!/bin/bash
cat /tmp/randomFile | (while read line
do
LINE="$LINE $line"
done && echo $LINE )
One more option:
#!/bin/bash
cat /some/file | while read line
do
var="abc"
echo $var | xsel -i -p # redirect stdin to the X primary selection
done
var=$(xsel -o -p) # redirect back to stdout
echo $var
EDIT:
Here, xsel is a requirement (install it).
Alternatively, you can use xclip:
xclip -i -selection clipboard
instead of
xsel -i -p
I got around this when I was making my own little du:
ls -l | sed '/total/d ; s/ */\t/g' | cut -f 5 |
( SUM=0; while read SIZE; do SUM=$(($SUM+$SIZE)); done; echo "$(($SUM/1024/1024/1024))GB" )
The point is that I make a subshell with ( ) containing my SUM variable and the while, but I pipe into the whole ( ) instead of into the while itself, which avoids the gotcha.
#!/bin/bash
OUTPUT="name1 ip ip status"
+export XCODE=0;
if [ -z "$OUTPUT" ]
----
echo "CRIT: $NAME - $STATUS"
- echo $((++XCODE))
+ export XCODE=$(( $XCODE + 1 ))
else
echo $XCODE
see if those changes help
Another option is to output the results into a file from the subshell and then read it in the parent shell. something like
#!/bin/bash
EXPORTFILE=/tmp/exportfile${RANDOM}
cat /tmp/randomFile | while read line
do
LINE="$LINE $line"
echo $LINE > $EXPORTFILE
done
LINE=$(cat $EXPORTFILE)

use of ssh variable in the shell script

I want to use the variables of ssh in shell script.
suppose I have some variable a whose value I got inside the ssh and now I want to use that variable outside the ssh in the shell itself, how can I do this ?
ssh my_pc2 <<EOF
<.. do some operations ..>
a=$(ls -lrt | wc -l)
echo \$a
EOF
echo $a
In the above example first echo print 10 inside ssh prints 10 but second echo $a prints nothing.
I would refine the last answer by defining some special syntax for passing the required settings back, e.g. "#SET var=value"
We could put the commands (that we want to run within the ssh session) in a cmdFile file like this:
a=`id`
b=`pwd`
echo "#SET a='$a'"
echo "#SET b='$b'"
And the main script would look like this:
#!/bin/bash
# SSH, run the remote commands, and filter anything they passed back to us
ssh user#host <cmdFile | grep "^#SET " | sed 's/#SET //' >vars.$$
# Source the variable settings that were passed back
. vars.$$
rm -f vars.$$
# Now we have the variables set
echo "a = $a"
echo "b = $b"
If you're doing this for lots of variables, you can add a function to cmdFile, to simplify/encapsulate your special syntax for passing data back:
passvar()
{
var=$1
val=$2
val=${val:-${!var}}
echo "#SET ${var}='${val}'"
}
a=`id`
passvar a
b=`pwd`
passvar b
You might need to play with quotes when the values include whitespace.
A script like this could be used to store all the output from SSH into a variable:
#!/bin/bash
VAR=$(ssh user#host << _EOF
id
_EOF)
echo "VAR=$VAR"
it produces the output:
VAR=uid=1000(user) gid=1000(user) groups=1000(user),4(adm),10(wheel)

SSH commands via bash script

I've been trying several fails to perform the following:
Basically, what I need is to execute several sequenced commands on a remote unix shell, such as setting environment variables with variables that I have on the script, move to a particular directory and run a script there and so on.
I've tried using a printf with the portion of the script and then piped the ssh command, but it didn't work quite well, also, I've read about the "ssh ... >> END" marker, which is great but since I'm using functions, it doesn't work well.
Do you have any thoughts?
Here's an excerpt of the code:
deployApp() {
inputLine=$1;
APP_SPECIFIC_DEPLOY_SCRIPT="$(echo $inputLine | cut -d ' ' -s -f1)";
BRANCH="$(echo $inputLine | cut -d ' ' -s -f2)";
JBOSS_HOME="$(echo $inputLine | cut -d ' ' -s -f3)";
BASE_PORT="$(echo $inputLine | cut -d ' ' -s -f4)";
JAVA_HOME_FOR_JBOSS="$(echo $inputLine | cut -d ' ' -s -f5)";
JAVA_HEAP="$(echo $inputLine | cut -d ' ' -s -f6)";
echo "DEPLOYING $APP_SPECIFIC_DEPLOY_SCRIPT"
echo "FROM BRANCH $BRANCH"
echo "IN JBOSS $JBOSS_HOME"
echo "WITH BASE PORT $BASE_PORT"
echo "USING $JAVA_HOME_FOR_JBOSS"
if [[ -n "$JAVA_HEAP" ]]; then
echo "WITH $JAVA_HEAP"
fi
echo
echo "Exporting jboss to $JBOSS_HOME"
ssh me#$SERVER <<END
cleanup() {
rm -f $JBOSS_SERVER/log/*.log
rm -Rf $JBOSS_SERVER/deploy/
rm -Rf $JBOSS_SERVER/tmp/
mkdir $JBOSS_SERVER/deploy
}
startJboss() {
cd $JBOSS_SERVER/bin
./jbossctl.sh start
return 0;
}
export JBOSS_HOME
export JBOSS_SERVER=$JBOSS_HOME/server/default
END
return 0;
}
With that "HERE" approach, I'm getting this error: "syntax error: unexpected end of file"
Thanks a lot in advance!
Just put the functions in your here document, too:
var="Hello World"
ssh user#host <<END
x() {
print "x function with args=$*"
}
x "$var"
END
[EDIT] Some comments:
You say "export JBOSS_HOME" but you never define a value for the variable in the here document. You should use export JBOSS_HOME="$JBOSS_HOME". BASH will take all text between the two END, replace all variables, and send the result to SSH for processing.
That also means the other side will see rm -f /path/to/jboss/server/*.log; the assignment to JBOSS_SERVER in the last line of the here document has no effect (at least not to the code in cleanup()).
If you want to pass $ unmodified to the remote server, you have to escape it with \: rm -f \$JBOSS_SERVER/log/*.log
You never call cleanup()
There is a } missing after return 0 to finish the definition of deployapp()
There may be other problems as well. Run the script with bash -x to see what the shell actually executes. You can also add echo commands in the here document to see what the values of the variables are or you can add set -x before cleanup() to get the same output as with bash -x but from the remote side.
I don't understand why you're using cut to split the arguments to your function. Just do
APP_SPECIFIC_DEPLOY_SCRIPT=$1
BRANCH=$2
JBOSS_HOME=$3
# etc.
If you don't quote your here document delimiter, the contents are expanded before they're sent to the server. That may be what you want. If you don't and you want all expansion to be done on the server side, then quote it like this:
ssh me#$SERVER <<'END'
# etc.
END
If you wan't a mixture, don't quote the delimiter, but do escape those things that you want delayed expansion for:
ssh me#$SERVER <<END
echo $EXPAND_ME_NOW \$EXPAND_ME_LATER
END
What are the export statements supposed to do? I can't see that they would have any effect at all.

Bash variable scope

Please explain to me why the very last echo statement is blank? I expect that XCODE is incremented in the while loop to a value of 1:
#!/bin/bash
OUTPUT="name1 ip ip status" # normally output of another command with multi line output
if [ -z "$OUTPUT" ]
then
echo "Status WARN: No messages from SMcli"
exit $STATE_WARNING
else
echo "$OUTPUT"|while read NAME IP1 IP2 STATUS
do
if [ "$STATUS" != "Optimal" ]
then
echo "CRIT: $NAME - $STATUS"
echo $((++XCODE))
else
echo "OK: $NAME - $STATUS"
fi
done
fi
echo $XCODE
I've tried using the following statement instead of the ++XCODE method
XCODE=`expr $XCODE + 1`
and it too won't print outside of the while statement. I think I'm missing something about variable scope here, but the ol' man page isn't showing it to me.
Because you're piping into the while loop, a sub-shell is created to run the while loop.
Now this child process has its own copy of the environment and can't pass any
variables back to its parent (as in any unix process).
Therefore you'll need to restructure so that you're not piping into the loop.
Alternatively you could run in a function, for example, and echo the value you
want returned from the sub-process.
http://tldp.org/LDP/abs/html/subshells.html#SUBSHELL
The problem is that processes put together with a pipe are executed in subshells (and therefore have their own environment). Whatever happens within the while does not affect anything outside of the pipe.
Your specific example can be solved by rewriting the pipe to
while ... do ... done <<< "$OUTPUT"
or perhaps
while ... do ... done < <(echo "$OUTPUT")
This should work as well (because echo and while are in same subshell):
#!/bin/bash
cat /tmp/randomFile | (while read line
do
LINE="$LINE $line"
done && echo $LINE )
One more option:
#!/bin/bash
cat /some/file | while read line
do
var="abc"
echo $var | xsel -i -p # redirect stdin to the X primary selection
done
var=$(xsel -o -p) # redirect back to stdout
echo $var
EDIT:
Here, xsel is a requirement (install it).
Alternatively, you can use xclip:
xclip -i -selection clipboard
instead of
xsel -i -p
I got around this when I was making my own little du:
ls -l | sed '/total/d ; s/ */\t/g' | cut -f 5 |
( SUM=0; while read SIZE; do SUM=$(($SUM+$SIZE)); done; echo "$(($SUM/1024/1024/1024))GB" )
The point is that I make a subshell with ( ) containing my SUM variable and the while, but I pipe into the whole ( ) instead of into the while itself, which avoids the gotcha.
#!/bin/bash
OUTPUT="name1 ip ip status"
+export XCODE=0;
if [ -z "$OUTPUT" ]
----
echo "CRIT: $NAME - $STATUS"
- echo $((++XCODE))
+ export XCODE=$(( $XCODE + 1 ))
else
echo $XCODE
see if those changes help
Another option is to output the results into a file from the subshell and then read it in the parent shell. something like
#!/bin/bash
EXPORTFILE=/tmp/exportfile${RANDOM}
cat /tmp/randomFile | while read line
do
LINE="$LINE $line"
echo $LINE > $EXPORTFILE
done
LINE=$(cat $EXPORTFILE)

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