I am trying to use a range operator to input a series of numbers for use in a PowerShell script. Here is my code:
$computers = servername + [1-9]
I would like the $computers variable to iterate the 1-9 i.e., servername1, servername 2, etc. etc. Any ideas?
1..9 | % { $computers += "servername$_`n" }
And the variable $computers will contain:
servername1
servername2
servername3
[...]
Try running only the 1..9 part on your command line and it'll be easier to see what's gonig on. You could also read up on arrays in PowerShell with Get-Help about_Arrays - look for the part about "range operator" near the beginning.
The following line of code does the same thing (and seems cleaner to me) and might be easier to understand as well.
$computers = 1..9 | foreach { "servername$_" }
Or simply 1..9 | foreach { "servername$_" } to see it on screen without saving it in a variable.
Related
I am trying to utilize a grep lookahead to get a value at the end of a line for a project I'm working on. The main issue I'm having is that I'm not sure how to use a shell variable in the grep lookahead syntax in cshell
Here's the gist of what I'm trying to do.
There will be a dogfile.txt with several lines listing the names of dogs in the format below
genericDog2033, pomeranian
genericDog2034, greatDane
genericDog2035, Doberman
I wanted a way of retrieving the breed of the dog after the comma on each line so I thought a grep lookahead might be a good way of doing it. The project I'm working on isn't so hard-coded however, so I have no way of knowing what genericDog number I am searching for. There will be a shell variable in a greater while loop which will have access to the dog name.
For example if I set the dogNumber variable to the first dog in the file like so:
set dogNumber = genericDog2033
I then try to access the value of dogNumber in the grep lookahead
set dogBreed = `cat File.txt | grep -oP '(?<=$dogNumber ,)[^ ]*'`
The problem with the line above is that I think grep is looking for the literal string "$dognumber ," in the file which obviously doesn't exist. Is there some sort of wrapper I can put around the shell variable so cshell knows that dogNumber is a variable? I'm also open to other methods of doing this. Any help would be appreciated, this is the literal last line of code I need to finish my project and I'm at my wits end.
Variable expansion only happens inside double quotes ("), and not single quotes ('):
% set var = 'hello'
% echo '$var'
$var
% echo "$var"
hello
Furthermore, you have an error in your regexp:
(?<=$dogNumber ,)[^ ]*
In your data, the space is after the comma, not before.
% set dogNumber = genericDog2033
% set dogBreed = `cat a | grep -oP "(?<=$dogNumber, )[^ ]*"`
% echo $dogBreed
pomeranian
The easiest way to debug this is to not use variables at all in the first place, and simply check if the grep works:
% grep -oP "(?<=genericDog2034 ,)[^ ].*" a
[no output]
Then first make the grep work with static data, add the variable to make that work, and then put it all together by assigning it to a variable.
I have two lists, one of which contains wildcards (in this case represented by *). I would like to compare the two lists and create an output of those that match, with each wildcard * representing a single character.
For example:
File 1
123456|Jane|Johnson|Pharmacist|janejohnson#gmail.com
09876579|Frank|Roberts|Butcher|frankie1#hotmail.com
092362936|Joe|Jordan|Joiner|joe#joesjoinery.com
928|Bob|Horton|Farmer|bhorton#farmernews.co.uk
File 2
1***6|Jane|Johnson|Pharmacist|janejohnson#gmail.com
09876579|Frank|Roberts|Butcher|f**1#hotmail.com
092362936|Joe|Jordan|J*****|joe#joesjoinery.com
928|Bob|Horton|Farmer|b*****n#f*********.co.uk
Output
092362936|Joe|Jordan|Joiner|joe#joesjoinery.com
928|Bob|Horton|Farmer|bhorton#farmernews.co.uk
Explanation
The first two lines are not considered matches because the number of *s is not equal to the number of characters shown in the first file. The latter two are, so they are added to output.
I have tried to reason out ways to do this in AWK and using Join, but I don't know any way to even start trying to achieve this. Any help would be greatly appreciated.
$ cat tst.awk
NR==FNR {
file1[$0]
next
}
{
# Make every non-* char literal (see https://stackoverflow.com/a/29613573/1745001):
gsub(/[^^*]/,"[&]") # Convert every char X to [X] except ^ and *
gsub(/\^/,"\\^") # Convert every ^ to \^
# Convert every * to .:
gsub(/\*/,".")
# Add line start/end anchors
$0 = "^" $0 "$"
# See if the current file2 line matches any line from file1
# and if so print that line from file1:
for ( line in file1 ) {
if ( line ~ $0 ) {
print line
}
}
}
$ awk -f tst.awk file1 file2
092362936|Joe|Jordan|Joiner|joe#joesjoinery.com
928|Bob|Horton|Farmer|bhorton#farmernews.co.uk
sed 's/\./\\./g; s/\*/./g' file2 | xargs -I{} grep {} file1
Explanation:
I'd take advantage of regular expression matching. To do that, we need to turn every asterisk * into a dot ., which represents any character in regular expressions. As a side effect of enabling regular expressions, we need to escape all special characters, particularly the ., in order for them to be taken literally. In a regular expression, we need to use \. to represent a dot (as opposed to any character).
The first step is perform these substitutions with sed, the second is passing every resulting line as a search pattern to grep, and search file1 for that pattern. The glue that allows to do this is xargs, where a {} is a placeholder representing a single line from the results of the sed command.
Note:
This is not a general, safe solution you can simply copy and paste: you should watch out for any characters, in your file containing the asterisks, that are considered special in grep regular expressions.
Update:
jhnc extends the escaping to any of the following characters: .\^$[], thus accounting for almost all sorts of email addresses. He/she then avoids the use of xargs by employing -f - to pass the results of sed as search expressions to grep:
sed 's/[.\\^$[]/\\&/g; s/[*]/./g' file2 | grep -f - file1
This solution is both more general and more efficient, see comment below.
Say I call Lua with this cmd:
luajit neuralnetwork.lua --satEpoch "somestring" --maxEpoch 50
How can I access this same cmd-line string from Lua?
I know about the arg table, but it removes all quotes from the original command string making it difficult to reconstruct:
{
"--maxEpoch"
"--satEpoch"
"50"
"somestring"
[-1] : "luajit"
[0] : "examples/neuralnetwork.lua"
}
If I can save the exact string to a file from within Lua, I can easily call it again later.
#peterpi is correct that the shell is interpreting the command and as a result stripping away the quotes. However, reconstructing the command exactly is not really necessary to have the shell interpret the command the same way as before.
For simple cases concatenating the arguments to the script is often enough:
local command = table.concat(arg, ' ', -1, #arg)
This will fail if the quotes are actually necessary, most commonly when an argument contains a space or shell character, so quoting everything is easy and somewhat more robust, but not pretty.
Here is an example with a Lua pattern to check for special (bash) shell characters and spaces to decide if and which quotes are necessary. It may not be complete but it handles filenames, most strings, and numbers as arguments.
local mod_arg = { }
for k, v in pairs(arg) do
if v:find"'" then
mod_arg[k] = '"'..v..'"'
elseif v:find'[%s$`><|#]' then
mod_arg[k] = "'"..v.."'"
else
mod_arg[k] = v
end
end
local command = table.concat(mod_arg, ' ', -1, #mod_arg)
print(command)
No doubt somebody will prove me wrong, but generally I don't think this is possible. It's the shell rather than luajit that takes the quotes away and chops the line up into individual tokens.
For example if I have file.txt with the following
object = {
'name' : 'namestring',
'type' : 'type',
'real' : 'yes',
'version' : '2.0',
}
and I want to extract just the version so the output is 2.0 how would I go about doing this?
I would suggest that grep is probably the wrong tool for this. Nevertheless, it is possible, using grep twice.
grep 'version' input.txt | grep -Eo '[0-9.]+'
The first grep isolates the line you're interested in, and the second one prints only the characters of the line that match the regex, in this case numbers and periods. For your input data, this should work.
However, this solution is weak in a few areas. It doesn't handle cases where multiple version lines exist, it's hugely dependent on the structure of the file (i.e. I suspect your file would be syntactically valid if all the lines were joined into a single long line). It also uses a pipe, and in general, if there's a way to achieve something with a pipe, and a way without a pipe, you choose the latter.
One compromise might be to use awk, assuming you're always going to have things split by line:
awk '/version/ { gsub(/[^0-9.]/,"",$NF); print $NF; }' input.txt
This is pretty much identical in functionality to the dual grep solution above.
If you wanted to process multiple variables within that section of file, you might do something like the following with awk:
BEGIN {
FS=":";
}
/{/ {
inside=1;
next;
}
/}/ {
inside=0;
print a["version"];
# do things with other variables too
#for(i in a) { printf("i=%s / a=%s\n", i, a[i]); } # for example
delete a;
}
inside {
sub(/^ *'/,"",$1); sub(/' *$/,"",$1); # strip whitespace and quotes
sub(/^ *'/,"",$2); sub(/',$/,"",$2); # strip whitespace and quotes
a[$1]=$2;
}
A better solution would be to use a tool that actually understands the file format you're using.
A simple and clean solution using grep and cut
grep version file.txt | cut -d \' -f4
This is for code:
set source_failed = `cat mine.log`
set dest_failed = `cat their.log`
foreach t ($source_failed)
set isdiff = 0
set sflag = 0
foreach t2 ($dest_failed)
if ($t2 == $t) then
set sflag = 1
break
endif
end
...
end
Problem is that the inner foreach loop runs okay for first few 10 iterations. After that iteration, suddenly I got
foreach: no match
Moreover, I am iterating over the array of strings, not files. What is the reason behind this error?
The problem is (probably) that mine.log and/or their.log contain special globbing characters, such as * or ?. The shell will try to expand this to a file. There are no matches for this accidental pattern, and hence the error "no match".
The easiest way to prevent this behaviour is to add set noglob to the top. From tcsh(1):
noglob If set, Filename substitution and Directory stack substitution
(q.v.) are inhibited. This is most useful in shell scripts
which do not deal with filenames, or after a list of filenames
has been obtained and further expansions are not desirable.
You can re-enable this behaviour by using set glob.
Alternativly, you can use :q. From tcsh(1):
Unless enclosed in `"' or given the `:q' modifier the results of variable
substitution may eventually be command and filename substituted.
[..]
When the `:q' modifier is applied to a substitution the variable will expand
to multiple words with each word sepa rated by a blank and quoted to
prevent later command or filename sub stitution.
But you need to be very careful about quoting when you use the variable. In the below example, the echo command will fail if you don't add quotes (set noglob is much easier):
set source_failed = `cat source`
foreach t ($source_failed:q)
echo "$t"
end