| gzcon {base} | R Documentation |
gzcon provides a modified connection that wraps an existing
connection, and decompresses reads or compresses writes through that
connection. Standard gzip headers are assumed.
gzcon(con, level = 6, allowNonCompressed = TRUE)
con |
a connection. |
level |
integer between 0 and 9, the compression level when writing. |
allowNonCompressed |
logical. When reading, should non-compressed input be allowed? |
If con is open then the modified connection is opened. Closing
the wrapper connection will also close the underlying connection.
Reading from a connection which does not supply a gzip magic
header is equivalent to reading from the original connection if
allowNonCompressed is true, otherwise an error.
The original connection becomes unusable: any object pointing to it will now refer to the modified connection.
When the connection is opened for reading, the input is expected to
start with the gzip magic header. If it does not and if
allowNonCompressed = TRUE (the default) the input is read as-is.
An object inheriting from class "connection". This is the same
connection number as supplied, but with a modified internal
structure. It has binary mode.
gzfile
## Uncompress a data file from a URL
z <- gzcon(url("http://www.stats.ox.ac.uk/pub/datasets/csb/ch12.dat.gz"))
# read.table can only read from a text-mode connection.
raw <- textConnection(readLines(z))
close(z)
dat <- read.table(raw)
close(raw)
dat[1:4, ]
## gzfile and gzcon can inter-work.
## Of course here one would used gzfile, but file() can be replaced by
## any other connection generator.
zz <- gzfile("ex.gz", "w")
cat("TITLE extra line", "2 3 5 7", "", "11 13 17", file = zz, sep = "\n")
close(zz)
readLines(zz <- gzcon(file("ex.gz", "rb")))
close(zz)
unlink("ex.gz")
zz <- gzcon(file("ex2.gz", "wb"))
cat("TITLE extra line", "2 3 5 7", "", "11 13 17", file = zz, sep = "\n")
close(zz)
readLines(zz <- gzfile("ex2.gz"))
close(zz)
unlink("ex2.gz")