I'm working on a script that has a number of functions in place which pull data from a few different arrays. We hope to keep the arrays individualized for reporting purposes. The information in the arrays does not change and the only thing different between each function is which array name is being used. Since all of the functions have 98% the same content I'm trying to pull them into 1 single array for simplified management.
The issue I'm facing though is that I'm not able to figure out the correct syntax to obtain the length of an array based on the array title that is passed in the function argument. I can't post the actual script, but here is a mock up that details a simplified version of what I'm testing with. I believe if we can get it working using the mock script below I can transfer the needed changes to the actual script.
array1=(
"item1 123"
"item2 456"
)
array2=(
"stockA qwe"
"stockB asd"
"stockC zxc"
)
test() {
local ref=${1}[#]
IFS=$'\n'; for i in ${!ref}; do echo $i ; done
}
test array1
test array2
The script above so far will echo the content of each array line based on argument 1 when the function and it's argument is called; which is working as needed. I've tried many different combinations such as len=${#${1}[#]} but I always receive a "bad substitution" error. The functions I mention before have while loops and for statements that use the array length to know when to stop, so being able to pull that information really ties it all together. What I'm hoping for is something like the flow below
I plan to continue my research on this, but thank you for any help and knowledge that can be provided!
-Cyanide
I think the only solution is to create a copy of the array, then take the length of that array:
local ref=${1}[#]
copy=( "${!ref}" )
len=${#copy[#]}
Since bash does not allow chaining of the parameter expansion operators, I know of no shorter way to use both ${#...} and ${!...} on the same line.
Related
I am new to R and I have a Perl Script in which I want to call a R Script, which calculates something for me (not important what in this context). I want to give as arguments an input file, an array which contains some numbers and a number for a total number of clusters. medoid.r is the name of my R Script.
my $R_out;
$R_out = qx{./script/medoid.r $output #cluster $NUMBER_OF_CLUSTERS}
My current R code looks like this. Right now I just print cluster to see what is inside.
args <- commandArgs(TRUE)
filename = args[1]
cluster = as.vector(args[2])
number_of_cluster = args[3]
matrix = read.table(filename, sep='\t', header=TRUE, row.names=1, quote="")
print(cluster)
Is it possible to give an array as an argument? How can I save it in R? Right now only the first number of the array is stored and printed, but I would like to have every number in a vector or something similar.
If you do this in Perl
$R_out = qx{./script/medoid.r $output #cluster $NUMBER_OF_CLUSTERS};
your command line will look similar to this
./scriptmedoid.r output 111 222 333 3
assuming that $output is 'output' and #clusters = (111, 222, 333).
If you want to read that in R, you need to assign all elements after the first one in args to cluster but the last one, and the last one to number_of_cluster. In Perl you can use shift and pop for that.
my #args = #_;
my $output = shift #args;
my $number = pop #args;
# now #args only contains the clusters
I don't know if those operators exist in R.
You cannot pass a full data structure unless you serialize it in some way.
In perl, qx will expect a string as an argument. You may certainly use an array to generate that string, but ultimately it will still be a string. You cannot "pass an array" to a system call, you can only pass command-line text/arguments.
Keep in mind, you are executing a system call running Rscript as a child process. The way you're describing the issue, there is no inter-process communication beyond the command line. Think of it this way: how would you type an array on the command line? You may have some textual way of representing an array, but you can't type an array on the command line. Arrays are stored and accessed in memory differently by various different languages, and thus are not really portable between two languages like you're suggesting.
One solution: all that said, there may be a simple solution for you. You haven't provided any information on the type of data you want to pass in your array. If it is simple enough, you may try passing it on the command line as delimited text, and then break it up to use in your Rscript.
Here is an Rscript that shows you what I mean:
args = commandArgs(trailingOnly=TRUE)
filename = args[1]
cluster <- c(strsplit(args[2],"~"))
sprintf("Filename: %s",filename)
sprintf("Cluster list: %s",cluster)
print("Cluster:")
cluster
sprintf("First Item: %s",cluster[[1]][1])
Save it as "test.r" and try executing it with "Rscript test.r test.txt one~two" and you'll get the following output (tested on Rscript 46084, OpenBSD):
[1] "Filename: test.txt"
[1] "Cluster list: c(\"one\", \"two\")"
[1] "Cluster:"
[[1]]
[1] "one" "two"
[1] "First Item: one"
So, all you'd have to do on the perl side of things is join() your array using "~" or any other delimiter- it is highly dependent on your data, and you haven't provided it.
Summary: re-think how you want to communicate between perl and Rscript. Consider sending the data as a delimited string (if it's the right size) and breaking it up on the other side. Look into IPC if that won't work, consider environment variables or other options. There is no way to send an array reference on the command-line.
Note: you may want to read up on security risks of different system calls in perl.
I'm trying to get an array containing the full current directory path in zsh. I'm currently using
local pwd="${PWD/#$HOME/~}"
pwd_list=(${(s:/:)pwd})
Which works except for one problem, it treats the starting / as a directory split too. I'd like my array to be like
/
usr
lib
php
instead of
usr
lib
php
I can see 2 ways of doing this but I'm unaware of how to do either in zsh. The first idea is to simple do a push and force a new element to the beginning (after the split).
The second, would be to alter the split to ignore the first / when parsing.
How can I resolve this to get an accurate directory path with minimal overhead into an array?
do you really need the first /? Assuming you're using a script to use the results of that, can't you just cd / to just start from there?
Anyways... is this what you want?
local pwd="${PWD/#$HOME/~}"
pwd_list=(${(s:/:)pwd})
pwd_list=('/' $pwd_list)
I think you're thinking about it slightly wrong. If you split "/usr/lib/php" on "/", you should get four elements, the first of which is an empty string. If you join those array elements back together with "/", you get the original path. Trying to think of the first element of "/" means you're treating the splitting inconsistently, which will make everything else harder.
So the problem really is that you're only getting three elements instead of four: the empty first element is getting dropped. You can fix that by quoting, like this:
local pwd="${PWD/#$HOME/~}"
pwd_list=( "${(s:/:)pwd}" )
(The extra space next to the outer parentheses isn't necessary, but it makes it a little easier to read.) You can even combine that into one expression:
pwd_list=( "${(s:/:)${PWD/#$HOME/~}}" )
I have an array which contains
commName[0]="ls"
commName[1]="date"
commName[2]="crontab"
commName[3]="uname"
commName[4]="hostname"
Now the array doesn't always contain these. Sometimes it can have more indices sometimes less. And the values are not always ls,date,... They can be different. Bottom line, I don't know the size nor the values of the array when I'm coding.
Every array value ls,date,... has its own unique address. So for example, ls would have /home/test/ and date would have /home/test/test2/ etc... These addresses need to be stored into a variable which will be used later on in the code. So I should have following variables according to the given array
$lsAddress
$dateAddress
$crontabAddress
$unameAddress
$hostnameAddress
Therefore, I need a way to make these variables (have in mind that I don't know ls,date,uname,....)
My approach was this
for ((j=0 ; j<${#commName[#]} ; j++))
do
set commName[$j]Nick="hi"
echo $(${commName[$j]}Nick)
done
What I expected this to do was to create new variables for every index of the array and set them equal to hi (just for test purposes) and then access those new variables.
Also, The new created variables Must be accessible anywhere. So, I can't have a temporary variable that keeps getting replaced.
However, this method isn't working... Is there any other way I can do this?
Use eval. Try this:
for ((j=0 ; j<${#commName[#]} ; j++))
do
param=`echo ${commName[$j]}Nick`
eval "$param=hi1"
eval "echo \$$param"
done
Use two parallel arrays, so that the entry in the command array matches with the corresponding entry in the address array.
commName[0]="ls"
commName[1]="date"
commName[2]="crontab"
commName[3]="uname"
commName[4]="hostname"
commAddress[0]="/home/test/" # ls
commAddress[1]="/home/test/test2" # date
# etc
Then, when you have a particular value of i, you know that ${commName[i]} and ${commAddress[i]} go together.
I recommend the two arrays, but you might also consider using bash's indirect parameter expansion instead.
$ commName[0]="ls"
$ lsAddress="/home/test"
$ name="${commName[0]}Address"
$ echo "${!name}"
/home/test
Two things, first this is my first question in this forum and I do apologise if the formating is all over the place. Second I have not written that many bash scripts, and it tend to be quite a long time between the scripts I produce.
That said, here is my question.
Is it possible to do something like this in bash (Clear array $array contains):
$array=()
Basically this is what I would like to do. I have a variable with array variable names in it:
array1=()
array2=()
arrayList="array1 array2"
# In a function far far away
for array in $arrayList
do
eval arr=("\"\${$array[#]\"")
for index in ${!arr[#]}
do
echo "${arr[$index]}"
done
# Here is the big "?", I like to clear the array that $array refers to.
$array=()
done
My arrays contain strings that include "" (space) and this is why I use the eval statement. Not sure it's needed but at least it's working. The script is more or less working as I want it too, but I need to clear the arrays in the $arrayList, and I rather not hardcode it somewhere, even though that would be easy.
Probably the simplest thing to do is just unset them. An unset variable will act identically to an empty array in most contexts, and unset $array ought to work fine.
You can't do $foo=bar ever -- that isn't how indirect assignments in bash work. Unfortunately, while being able to do indirect array assignments is an available feature in ksh93, it isn't a formally documented available feature in bash.
Quoting BashFAQ #6 (which should be read in full if you're interested in knowing more about using indirect variables in general):
We are not aware of any trick that can duplicate that functionality in POSIX or Bourne shells (short of using eval, which is extremely difficult to do securely). Bash can almost do it -- some indirect array tricks work, and others do not, and we do not know whether the syntax involved will remain stable in future releases. So, consider this a use at your own risk hack.
# Bash -- trick #1. Seems to work in bash 2 and up.
realarray=(...) ref=realarray; index=2
tmp="$ref[$index]"
echo "${!tmp}" # gives array element [2]
# Bash -- trick #2. Seems to work in bash 3 and up.
# Does NOT work in bash 2.05b.
tmp="$ref[#]"
printf "<%s> " "${!tmp}"; echo # Iterate whole array.
However, clearing is simpler, as unset $array will work fine.
array=()
It clears the array. I guess that is what you wanted..
Is there a way to (ab)use the tcl C-API to 'parse' a string, doing all the replacement (including sub commands in square brackets), but stopping before actually evaluating the resulting command line?
What I'm trying to do is create a command (in C, but I'll consider doing a tcl-wrapper, if there's an elegant way to do it there) which takes a block as a parameter (i.e. curly-braces-quoted-string). I'd like to take that block, split it up and perform substitutions in the same way as if it was to be executed, but stop there and interpret the resulting lines instead.
I've considered creating a namespace, where all valid first-words are defined as commands, however this list is so vast (and pretty much dynamic) so it quickly becomes too cumbersome. I also tried this approach but with the unknown command to intercept the different commands. However, unknown is used for a bunch of stuff, and cannot be bound to a namespace, so I'd have to define it whenever I execute the block, and set it back to whatever it was before when I'm done, which feels pretty shaky. On top of that I'd run the risk (fairly low risk, but not zero) of colliding with an actual command, so I'd very much prefer to not use the unknown command.
The closest I can get is Tcl_ParseCommand (and the rest of the family), which produces a parse tree, which I could manually evaluate. I guess I'll resort to doing it this way if there's no better solution, but I would of course prefer it, if there was an 'official' way..
Am I missing something?
Take a look at Tcl_SubstObj. It's the C equivalent of the [subst] command, which appears to be what you're looking for.
As you indicated in your comment, subst doesn't quite do what you're looking to do. If it helps, the following Tcl code may be what you're looking for:
> set mydata {mylist item $listitem group item {$group item}}
> set listitem {1 2 3}
> subst $mydata ;# error: can't read "group": no such variable
> proc groupsubst {data} {
return [uplevel 1 list $data]
}
> groupsubst $mydata ;# mylist item {1 2 3} group item {$group item}