Hey all,
what is wrong with this command:
system2("echo", env = c(VAR = "Hello World"), args =
c("$VAR"))
I am a bit confused, as help("system2") writes about the env option:
> character vector of name=value strings to set environment variables.
Is this option buggy, or am I using it just wrong?
Thanks for your help
Henning
Probably not broken, just hard to get the quoting right? Or it does
not work with echo?
It is surely hard to get it right, I have been trying for 15 minutes.I
am pretty sure that the correct form is env =
"VAR='Hello-World'" but
spaces and other special characters might cause trouble. E.g. this
works, but only without spaces (px is an internal tool for testing,
that can get an env var, and it is portable):
? px <- processx:::get_tool("px")
? system2(px, c("getenv", "VAR"), env = "VAR=foo")
foo
? system2(px, c("getenv", "VAR"), env = c(VAR="Hello
World"))
sh: Hello: command not found
Warning message:
In system2(px, c("getenv", "VAR"), env = c(VAR = "Hello
World")) :
error in running command
Somebody with more system2() experience can probably fix this, but
here is an alternative, using the processx package:
? processx::run(px, c("getenv", "VAR"), env =
c(Sys.getenv(), VAR "Hello World"))
$status
[1] 0
$stdout
[1] "Hello World\n"
$stderr
[1] ""
$timeout
[1] FALSE
For processx, you don't need to quote anything (i.e. command,
arguments or env vars), because it does not
use an intermediate shell.
Disclaimer: I am an author of processx.
Gabor
On Tue, Mar 19, 2019 at 9:28 AM Henning Bredel <h.bredel at gmx.de>
wrote:>
> Hey all,
>
> what is wrong with this command:
>
> system2("echo", env = c(VAR = "Hello World"), args =
c("$VAR"))
>
> I am a bit confused, as help("system2") writes about the env
option:
>
> > character vector of name=value strings to set environment variables.
>
> Is this option buggy, or am I using it just wrong?
>
> Thanks for your help
>
> Henning
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
You are using it wrong. It wants strings of the form "name=value", not a character vector with names as labels. So this is closer to the mark:> system2("echo", env = c("VAR='Hello World'"), args = c("$VAR"))>However, as you see it doesn't work as intended. The problem is that the $-substitution refers to the environment of the shell executing the command. I.e. this does not work from a terminal command line either: pd$ VAR="foo" echo $VAR pd$ Or even pd$ VAR="bar" pd$ VAR="foo" echo $VAR bar What you need is something like (NB: single quotes!) pd$ VAR="foo" sh -c 'echo $VAR' foo So:> system2("sh", env = c("VAR='Hello World'"), args = c("-c 'echo $VAR'"))Hello World -pd> On 18 Mar 2019, at 17:28 , Henning Bredel <h.bredel at gmx.de> wrote: > > Hey all, > > what is wrong with this command: > > system2("echo", env = c(VAR = "Hello World"), args = c("$VAR")) > > I am a bit confused, as help("system2") writes about the env option: > >> character vector of name=value strings to set environment variables. > > Is this option buggy, or am I using it just wrong? > > Thanks for your help > > Henning > > ______________________________________________ > R-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel-- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Office: A 4.23 Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com
On Tue, Mar 19, 2019 at 9:59 AM peter dalgaard <pdalgd at gmail.com> wrote: [...]> What you need is something like (NB: single quotes!) > > system2("sh", env = c("VAR='Hello World'"), args = c("-c 'echo $VAR'")) > Hello WorldJust out of curiosity, do you think it is possible to make this portable, assuming sh is available? On Windows it gives> system2("sh", env = c("VAR='Hello World'"), args = c("-c 'echo $VAR'"))/rtools34/bin/sh: VAR=Hello World: No such file or directory Warning message: running command '"sh" VAR='Hello World' -c 'echo $VAR'' had status 127 G.
Okay, thanks for clarification. On 3/19/19 10:51 AM, peter dalgaard wrote:> You are using it wrong. It wants strings of the form "name=value", not a character vector with names as labels. So this is closer to the mark: > >> system2("echo", env = c("VAR='Hello World'"), args = c("$VAR")) > >> > > However, as you see it doesn't work as intended. The problem is that the $-substitution refers to the environment of the shell executing the command. I.e. this does not work from a terminal command line either: > > pd$ VAR="foo" echo $VAR > > pd$ > > Or even > > pd$ VAR="bar" > pd$ VAR="foo" echo $VAR > bar > > What you need is something like (NB: single quotes!) > > pd$ VAR="foo" sh -c 'echo $VAR' > foo > > So: > >> system2("sh", env = c("VAR='Hello World'"), args = c("-c 'echo $VAR'")) > Hello World > > -pd > >> On 18 Mar 2019, at 17:28 , Henning Bredel <h.bredel at gmx.de> wrote: >> >> Hey all, >> >> what is wrong with this command: >> >> system2("echo", env = c(VAR = "Hello World"), args = c("$VAR")) >> >> I am a bit confused, as help("system2") writes about the env option: >> >>> character vector of name=value strings to set environment variables. >> >> Is this option buggy, or am I using it just wrong? >> >> Thanks for your help >> >> Henning >> >> ______________________________________________ >> R-devel at r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel >