I am unable to print positional parameters using this shell command: echo $1.
I am using it as following two commands:
% set hi how are you
% echo $1
Nothing get out of the command, but hi should be print.
In csh, you need to assign to the argv array:
> set argv=(hi how are you)
> echo $1
hi
Explanation:
argv is an array variable which contains the command line argument list (the 0th argument is name as the shell was invoked and the other start from 1th index). Variables $0 - $n also contain values of the arguments . So $argv[1] is the same as $1. To assign to an array variable, you can use either set arr=(value1 value2) or set arr[1] = value1.
set value1 value2 would work in bash, but csh is meant to be similar to the C language, therefore the argv array is used (read a little about C program command line arguments if you don't know why).
But in csh, this: set first second means assigning an empty (null) value to the variables first and second.
Related
funtion.bat echo variables
set "Var1=%1"
set "Var2=%2"
set "Var3=%3"
echo %Var1% %Var2% %Var3%
I use a batch that calls this function by passing 3 arguments
call function.bat blabla= argument2 TEST.txt
As you see my first argument has an equal sign in it. But I want to use it as a string and not as an operator.
When I run the batch this is the result that I get:
blabla
argument2
TEST.txt
This is the result that I want:
blabla=
argument2
TEST.txt
Does anyone have an idea of how to get "blabla="?
From cmd /? in cmd:
The special characters that require quotes are:
<space>
&()[]{}^=;!'+,~ `
As you can see, you should quote almost everything that contains = because it is used as a separator. You should run your batch file with the command:
call function.bat "blabla=" "argument2" "TEST.txt"
in cmd and then remove the double quotes for each argument using the following code (the ~ modifier):
set "Var1=%~1"
set "Var2=%~2"
set "Var3=%~3"
echo %Var1% %Var2% %Var3%
and it should work. This way is recommended for best practice. Do it always.
I want to execute an external program in lua. Usually this can be done with
os.execute("run '"..arg0.."' 'arg1' arg2")
The problem with this approach is if I want to pass user input as string to an external program, user input could be '; evil 'h4ck teh system' ' and the script from above would execute like this:
/bin/bash -c "run ''; evil 'h4ck teh system' '' 'arg1' arg2"
Another problem occurs when I have '$var' as argument and the shell replaces this with its environment variable. In my particular case I have something like [[program 'set title "$My Title$"']] – so nested strings – and program parses "$My Title$" (with escape sequences) differently than '$My Title$' (as it is). Because I want to set the title as it, the best way is to have arguments like this: 'My Title'. But now the command have to be:
os.execute([[run "set title '$My Title$'"]])
But now – as I said – $My will be replaced with an empty string, because the environment does not know any variable named $My and because, I never wanted it to be replaced.
So I am looking for the usual approach with
execv("run", {"set title '"..arg0.."'", arg1, arg2})
local safe_unquoted = "^[-~_/.%w%%+,:#^]*$"
local function q(text, expand) -- quoting under *nix shells
-- "expand"
-- false/nil: $var and `cmd` must NOT be expanded (use single quotes)
-- true: $var and `cmd` must be expanded (use double quotes)
if text == "" then
text = '""'
elseif not text:match(safe_unquoted) then
if expand then
text = '"'..text:gsub('["\\]', '\\%0')..'"'
else
local new_text = {}
for s in (text.."'"):gmatch"(.-)'" do
new_text[#new_text + 1] = s:match(safe_unquoted) or "'"..s.."'"
end
text = table.concat(new_text, "\\'")
end
end
return text
end
function execute_commands(...)
local all_commands = {}
for k, command in ipairs{...} do
for j = 1, #command do
if not command[j]:match"^[-~_%w/%.]+$" then
command[j] = q(command[j], command.expand)
end
end
all_commands[k] = table.concat(command, " ") -- space is arguments delimiter
end
all_commands = table.concat(all_commands, ";") -- semicolon is commands delimiter
return os.execute("/bin/bash -c "..q(all_commands))
end
Usage examples:
-- Usage example #1:
execute_commands(
{"your/program", "arg 1", "$arg2", "arg-3", "~/arg4.txt"},
{expand=true, "echo", "Your program finished with exit code $?"},
{"ls", "-l"}
)
-- The following command will be executed:
-- /bin/bash -c 'your/program '\''arg 1'\'' '\''$arg2'\'' arg-3 ~/arg4.txt;echo "Your program finished with exit code $?";ls -l'
$arg2 will NOT be expanded into value because of single quotes around it, as you required.
Unfortunately, "Your program finished with exit code $?" will NOT be expanded too (unless you explicitly set expand=true).
-- Usage example #2:
execute_commands{"run", "set title '$My Title$'", "arg1", "arg2"}
-- the generated command is not trivial, but it does exactly what you need :-)
-- /bin/bash -c 'run '\''set title '\''\'\'\''$My Title$'\''\'\'' arg1 arg2'
An argument is passed to bash script from outside and is read within bash file. Looks like as follows:
#following is the point from where the argument is passed to config.sh
controller.vm.provision :shell, path: 'shell/config.sh', keep_color: true, privileged: false, :args => ip
inside the config.sh reading the argument. The argument "ip" is somewhat like following:
ip = "10.12.153.26" "10.12.153.25" "10.12.153.24"
Now i want to iterate over the above argument inside the bash. so doing as follows:
array=($1) //please note $1="10.12.153.26" "10.12.153.25" "10.12.153.24"
for i in ${array[#]}
do
echo $i //it is iterated only once and output is "10.12.153.26" "10.12.153.25" "10.12.153.24"
done
So the output i am getting only once and is complete argument as it is but i want it to get displayed one by one so, that i can even use the single value separately for some other purpose. So, please suggest how can i have this?
If you want to split the value on spaces, you can do like this:
set -- $1
for i; do
echo $i
done
If the value of $i is "10.12.153.26" "10.12.153.25" "10.12.153.24",
then this will output:
"10.12.153.26"
"10.12.153.25"
"10.12.153.24"
To get rid of the double-quotes, you could use parameter expansion:
set -- $1
for i; do
echo ${i//\"/}
done
I have a doubt. When i declare a value and assign to some variable, I don't know how to reassign the same value to another variable. See the code snippet below.
#/bin/sh
#declare ARG1 to a
a=ARG1
#declaring $a to ARG2
ARG2=$`$a`
echo "ARG 2 = $ARG2"
It should display my output as
ARG 2 = ARG1
...but instead the actual output is:
line 5: ARG1: command not found
ARG 2 = $
To assign the value associated with the variable dest to the variable source, you need simply run dest=$source.
For example, to assign the value associated with the variable arg2 to the variable a:
a=ARG1
arg2=$a
echo "ARG 2 = $arg2"
The use of lower-case variable names for local shell variables is by convention, not necessity -- but this has the advantage of avoiding conflicts with environment variables and builtins, both of which use all-uppercase names by convention.
You may also want to alias rather than copy the variable. For example, if you need mutation. Or if you want to run a function multiple times on different variables. Here's how it works
Example:
C=cat
declare -n VAR=C
VAR+=" says Hi"
echo "$C" # prints "cat says Hi"
Example with arrays/dictionaries:
A=(a a a)
declare -n VAR=A # "-n" stands for "name", e.g. a new name for the same variable
VAR+=(b)
echo "${A[#]}" # prints "a a a b"
That is, VAR becomes effectively the same as the original variable. Instead of copying, you're adding an alias. Here's an example with functions:
function myFunc() {
local -n VAR="$1"
VAR="Hello from $2"
echo "I've set variable '$1' to value '$VAR'"
}
myFunc Inbox Bob # I've set variable 'Inbox' to value 'Hello from Bob'
myFunc Luke Leia # I've set variable 'Luke' to value 'Hello from Leia'
echo "$Luke" # Hello from Leia
Whether you should use these approaches is a question. Generally, immutable code is easier to read and to reason about (in almost any programming language). However, sometimes you really need to get stuff done in a certain way. Hope this answer helps you then.
I have a an old csh script (which hopefully I have time to rewrite in perl) which has a series of variables wmr1, wmr2 ... wmr24. What I would like to do is echo the values of each variable using a foreach loop eg
foreach i(`seq 1 24`)
echo ${wmr$i}
end
Can this be done in csh or using a perl one liner (using a symbolic refernce?)? I am not sure how to combine the integer $i with wmr and output the value of $wmr1 $wmr2 etc. echo ${wmr$i} in the loop gives me the error Missing }.
You can try this
foreach i (`seq 1 24`)
eval 'echo $wm'$i
end
The eval statement will evaluate the string given to it.
So replace echo with any other command you may want to use.