call_system <- function(command, args, env=character(), max_lines=20,
p=0.8, stdout=TRUE, stderr=TRUE, locate_command=TRUE) {
if (locate_command) {
command <- Sys_which(command)
}
res <- suppressWarnings(system2(command, args,
env=env, stdin="",
stdout=stdout, stderr=stderr))
## TODO: need to better allow stdout/stderr to *not* be captured.
ok <- attr(res, "status")
if (!is.null(ok) && ok != 0) {
max_nc <- getOption("warning.length")
cmd <- paste(c(env, shQuote(command), args), collapse = " ")
msg <- sprintf("Running command:\n %s\nhad status %d", cmd, ok)
errmsg <- attr(cmd, "errmsg")
if (!is.null(errmsg)) {
msg <- c(msg, sprintf("%s\nerrmsg: %s", errmsg))
}
sep <- paste(rep("-", getOption("width")), collapse="")
## Truncate message:
if (length(res) > max_lines) {
n <- ceiling(max_lines * p)
res <- c(head(res, ceiling(max_lines - n)),
sprintf("[[... %d lines dropped ...]]", length(res) - max_lines),
tail(res, ceiling(n)))
}
## compute the number of characters so far, including three new lines:
nc <- (nchar(msg) + nchar(sep) * 2) + 3
i <- max(1, which(cumsum(rev(nchar(res) + 1L)) < (max_nc - nc)))
res <- res[(length(res) - i + 1L):length(res)]
msg <- c(msg, "Program output:", sep, res, sep)
stop(paste(msg, collapse="\n"))
}
invisible(res)
}
Sys_which <- function(name) {
if (length(name) != 1L) {
stop("'name' must be a scalar")
}
ret <- Sys.which(name)
if (ret == "") {
stop(sprintf("%s not found in $PATH", name))
}
ret
}
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