Questions tagged [eval]
The eval tag has no usage guidance.
46
questions
2
votes
2answers
103 views
building an alias from a function
I need a lot of different aliases to create ssh tunnels to different servers. To give you a few of them:
alias tunnel_1='autossh -M 20000 -N -L 8080:localhost:8080 -N -L 9200:localhost:9200 -N -L ...
9
votes
2answers
228 views
Behaviour of “eval” under “set -e” in conditional expression
Consider the commands
eval false || echo ok
echo also ok
Ordinarily, we'd expect this to execute the false utility and, since the exit status is non-zero, to then execute echo ok and echo also ok.
...
2
votes
1answer
174 views
How to execute something in current shell [duplicate]
I want to create a bash script or something similar that I can execute in the current shell:
echo '#!/bin/bash
export foo="bar" ' > zoom.sh
but if I want to run this script in the current ...
0
votes
1answer
172 views
Weird behavior of su command
Everytime I run su command on this box, I constantly see the weird messages below. Switching user do eventually continue, but why are these messages showing?
<Server>:~ # su -
-bash: eval: line ...
1
vote
1answer
50 views
Why does this bash idiom require eval?
Why does this produces _results=""...
_results="$( grep ${_gopts[@]} )"
And this produces the desired _results (list of SSHFS entries in fstab)...
_results="$( eval grep ${_gopts[@]} )"
The _gopts ...
0
votes
1answer
43 views
How to check “eval” command?
My code
docker-machine create --driver virtualbox dev
VBoxManage list vms
"minikube" {9c326ed5-faf4-42fe-acda-bf3a283f1a74}
"kalinew" {de6de631-0d51-4638-b967-66db463cbf05}
"dev" {84a116bf-02b9-...
1
vote
3answers
650 views
Get return code of first piped command using eval?
I wish to execute different commands and check the return code afterwards before moving to the next steps in the script. At the same time I also wish to log the output of the executed commands to a ...
0
votes
1answer
692 views
Trying to export a path from inside a bash script [duplicate]
I am trying to put my whole environment set up into a single bash file. I am only hitting one issue. When I try to export a new path from inside the file it is not setting the path in the environment ...
0
votes
2answers
332 views
eval ssh command in variable
I am trying to execute commands via ssh remotely. But I have the calling command saved as variable such as:
SSH_CMD="ssh -i path_to/identity"
SSH_USER=user
SSH_DST=server
dir1=dir1
dir2=dir2
now if ...
5
votes
1answer
751 views
File with parentheses/brackets in working directory causes eval error
I encountered a strange bug today, when running a script in a directory containing a directory with parentheses in it, such as a().
Minimal working example
I managed to reduce the bug to the ...
-3
votes
2answers
95 views
Loop through filenames without eval [closed]
In a shell script, if we want to loop over certain filenames, which we would get by shell globbing, as for example all MKV-files in all sub-directories starting with string "Example" – how can we do ...
0
votes
2answers
652 views
Eval and exec with variable substitution
I'd like to execute a statement to start a server. For that I have an environment variable to determine which server is to be started. I was given this command as a starting point:
eval "exec ...
2
votes
2answers
263 views
Bash: How to kill eval if the process that receives its output terminates
I have a little ugly bash script on my Ubuntu machine that contains the lines:
search_command="find -L $(printf "%q" "$search_folder") \( ! -regex '.*/\..*/..*' \) -mindepth 1 2> /dev/null"
for i ...
0
votes
1answer
890 views
dollar sign inside eval string in bash
I have hundreds of sub-directories which contain a dollar sign (i.e., $)
as the 1st character in their names, each of which needs to be visited.
These sub-directories can not be renamed. The bash ...
1
vote
1answer
117 views
zsh: A prefix function that runs the rest of the line with no alias expansion
I am thinking of:
function noalias() {
setopt localoptions noexpandalias
"$@"
}
But I don't know what the last line should be. eval "${*:q}"? eval "$@"? eval "${@:q}"? "${@:q}"? ${@:q}? $@? (...
2
votes
2answers
202 views
Does `eval` apply the shell to the redirection part of the following command?
When use eval on a command, does eval apply the shell twice to the redirection part of the command?
Suppose the filename in the redirection contains a whitespace, if eval applies all the steps of ...
1
vote
2answers
988 views
Why is eval not working with command substitution? [closed]
I have this command
$("${DIR}/test.py" "$1")
the output of which is
export SOME_VAR="hello world"
export ANOTHER_VAR="hello"
But eval $("${DIR}/test.py" "$1")
seems to do nothing. What am I ...
6
votes
1answer
2k views
eval vs. pipe through bash
What is the difference between using:
eval 'echo "foo"'
and
echo 'echo "foo"' | bash
is there any?
-3
votes
1answer
116 views
Eval not working
i try run this code to get random number but eval seems not working
this is my code
#!/bin/bash
# Sequencia alfanumerica de 12 carateres aleatoriamente (maiusculas e minusculas)
file="/home/...
1
vote
2answers
78 views
cksum files using substituted variable string as a pattern
Can I avoid eval in the below example or is there no other way?
The list of files on variable is dynamic, and I want to cksum all of them.
There are many other files in the directory, but they should ...
2
votes
3answers
140 views
Get contents of passing string from a script
I would like to get, in the output, the content of KW0_TEXT and KW1_TEXT from the "for" of this script:
#!/bin/sh
STRS=" KW0 KW1 "
KW0_TEXT="text text text"
KW1_TEXT="text text text text"
for str ...
1
vote
1answer
1k views
Will “dircolors” work here instead of “ eval `”dircolors`“` ”?
I was checking .bashrc to set colors for ls comand and found this
export SHELL='/bin/bash'
export LS_OPTIONS='--color=auto'
eval "`dircolors`"
alias ls='ls $LS_OPTIONS'
Will there be any problem ...
0
votes
3answers
702 views
diff two files from a command output [closed]
I have a bunch of xml file in the current directory.
Problem 1.
As far as I have read eval returns the results and stores it in a variable.
But I get an error with the below command
find ./ -name '...
1
vote
2answers
3k views
Why is using eval necessary to pass quoted arguments
I have the following example.
#!/bin/bash
ARGUMENTS="-executors 1 -description \"The Host\" "
# call1
# error: parameter Host" is not allowed
java -jar swarm-client.jar $ARGUMENTS
# call2
# ...
6
votes
2answers
12k views
return value from eval
The bash manual states:
eval [arg ...]
The args are read and concatenated together into a single com-
mand. This command is then read and executed by the shell, and
...
6
votes
4answers
23k views
bash + read variables & values from file by bash script
I have the following file variable and values
# more file.txt
export worker01="sdg sdh sdi sdj sdk"
export worker02="sdg sdh sdi sdj sdm"
export worker03="sdg sdh sdi sdj sdf"
I perform source in ...
1
vote
2answers
399 views
eval not evaluating echo? [duplicate]
I'm trying to write something that stores an API access token in a bash variable, so I'm modelling it on ssh-agent, where you use eval.
ssh-agent
If you run ssh-agent by itself, it outputs something ...
16
votes
4answers
24k views
How can I list all user names and/or home directories?
I want to list all the users dirs on the machine.Usually, I will do:
ls -l /home
But I use it in a script that will be deployed on others machines and maybe on that machines they don't call it home (...
1
vote
1answer
239 views
how to evaluate an dynamically generated if elif else statement in shell
im having trouble getting a dynamically generated shell function to evaluate properly (by evaluate i mean "eval" command)
this is the desired statement to be evaluated when ran (except the output ...
4
votes
2answers
2k views
Bash: Why is used eval and shift in a script that parses command line arguments?
As I was looking this answer https://stackoverflow.com/a/11065196/4706711 in order to figure out on how to use parameters like --something or -s some questions rised regarding the answer's script :
#!...
0
votes
1answer
46 views
Evaluate part of a text line
I have an expression of the form @(<date calculation>) that I want to replace with the result of date +%s --date "now<date calculation>". So for example @(-1 day) would be replaced with ...
75
votes
1answer
21k views
Why eval the output of ssh-agent?
In order to run ssh-agent I have to use
eval $(ssh-agent)
Why do I have to eval the output of ssh-agent?
Why isn't it designed so that I can just run it?
Note: Backticks (`) removed as they are ...
0
votes
1answer
103 views
Process Substitution (e. g. $(somecommand) ) In A Nutshell
On my shell from home directory on mac, I run the following
eval "ls" and this just shows me the directories. But if I run
eval "$(ls)" I get the following output:
zsh: command not found: ...
2
votes
1answer
1k views
Can bash expand a quoted and/or escaped string variable into words?
I have a bash shell variable containing a string formed of multiple words delimited by whitespace. The string can contain escapes, such as escaped whitespace within a word. Words containing whitespace ...
0
votes
1answer
591 views
why doesn't eval declare in a function work in bash?
Tracking down strange behavior a bash script resulted in the following MWE:
set -o errexit
set -o nounset
set -x
my_eval()
{
eval "$1"
}
my_eval "declare -A ASSOC"
ASSOC[foo]=bar
echo success
...
2
votes
3answers
888 views
Using the eval command twice
Suppose:
a=b; b=c; c=d
Then eval echo \$$a produces the output:
c
If we want to extract the output d using just input a, I tried the following way:
(i) eval echo \$(eval echo \$$a) produces the ...
0
votes
3answers
888 views
Is eval implemented by creating a shell process to evaluate the following command?
In eval <command>, how does eval evaluate the following command?
does eval create a shell subprocess to evaluate <command>?
If not, does eval rely on the current shell process to ...
asked Jul 19 '16 at 12:16
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4
votes
1answer
261 views
How to deal with insecurity of `eval` evaluating external input in a script?
Binaryzebra said
this script is evaluating external input, a highly insecure practice.
What are some ways to deal with or even replace eval evaluating external inputs in a script?
Thanks.
asked Jul 19 '16 at 11:45
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67.1k100 gold badges321 silver badges608 bronze badges
0
votes
1answer
744 views
script set command output to variable [duplicate]
I'm writing a simple script that prompts the user for information and saves it as a variable to be passed as arguments in another command. One of the variables stores a path which may include a space. ...
7
votes
1answer
4k views
How to save an alias of an eval $(other_comand) command
I've been using docker for a while and there's a command I write each time I boot up my docker:
eval $(docker-machine env)
I know eval shouldn't be used unless necessary, but it's mentioned by the ...
0
votes
2answers
2k views
Error when eval a for-loop
I am writing a script which accepts two arguments:
#! /bin/bash
eval for i in {$1..$2}; do echo $i; done
I run it like:
$ ./myscript 0002 0010
syntax error near unexpected token `do'
Why is ...
asked Apr 23 '16 at 1:33
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5
votes
3answers
6k views
Why and when should eval use be avoided in shell scripts? [duplicate]
Many answers and comments on this site mention that one should generally avoid using eval in shell scripts. Often these comments are addressed to beginners.
I've seen mention of security issues and ...
-3
votes
1answer
197 views
What is the purpose of eval? [duplicate]
What is the purpose of running a command with eval?
What kinds of commands can eval run? I find it can run builtin command, external executable command, pipeline, script. Can it run all kinds of ...
asked Apr 22 '16 at 19:46
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0
votes
1answer
110 views
Why does parameter expansion happen before brace expansion in this example?
From https://unix.stackexchange.com/a/7739/674, why does parameter expansion happen before brace expansion in the following example?
eval rm foo.{$ext0..$extN}
asked Apr 22 '16 at 15:24
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67.1k100 gold badges321 silver badges608 bronze badges
3
votes
1answer
388 views
What does eval X=\$$i mean in UNIX?
I have a small script with the following lines
echo mom,dad |awk -F, '{print $1,$2}' | while read VAR1 VAR2
do
for i in VAR1 VAR2
do
eval X=\$$i
echo $X
done
done
OUTPUT:
mom
dad
What ...
197
votes
7answers
513k views
What is the “eval” command in bash?
What can you do with the eval command? Why is it useful? Is it some kind of a built-in function in bash? There is no man page for it..
