RCurl:在 Rgui 中显示进度表

Question

使用 R.exe 或 Rterm.exe，这提供了一个极好的进度表。

page=getURL(url="ftp.wcc.nrcs.usda.gov", noprogress=FALSE) 

在 Rgui 中，我仅限于:

page=getURL(url="ftp.wcc.nrcs.usda.gov", 
            noprogress=FALSE, progressfunction=function(down,up) print(down))

它提供了一组非常有限的下载信息。

有什么办法可以改善吗？

Answer 1

I start doubting that with standard R commands it is possible to reprint overwriting the current line, which is what RCurl does in non-GUI mode.

我很高兴地告诉大家我错了。至少对于单行，\r 可以做到这一点。事实上:

conc=function(){
    cat(" abcd")
    cat(" ABCD", '\n')

}
conc()

# abcd ABCD 

但是:

over=function(){
    cat(" abcd")
    cat("\r ABCD", "\n")
}
over()

# ABCD

鉴于此，我编写了这个 progressDown 函数，它可以监视下载状态重写始终在同一行:

library(RCurl) # Don't forget

### Callback function for curlPerform
progressDown=function(down, up, pcur, width){
    total=as.numeric(down[1]) # Total size as passed from curlPerform
    cur=as.numeric(down[2])   # Current size as passed from curlPerform
    x=cur/total
    px= round(100 * x)
    ## if(!is.nan(x) &&  px>60) return(pcur) # Just to debug at 60%
    if(!is.nan(x) && px!=pcur){
        x= round(width * x)
        sc=rev(which(total> c(1024^0, 1024^1, 1024^2, 1024^3)))[1]-1
        lb=c('B', 'KB', 'MB', 'GB')[sc+1]
        cat(paste(c(
            "\r  |", rep.int(".", x), rep.int(" ", width - x),
            sprintf("| %g%s of %g%s %3d%%",round(cur/1024^sc, 2), lb, round(total/1024^sc, 2), lb, px)),
                  collapse = ""))
        flush.console() # if the outptut is buffered, it will go immediately to console
        return(px)
    }
    return(pcur)
}

现在我们可以使用 curlPerform 的回调

curlProgress=function(url, fname){
    f = CFILE(fname, mode="wb")
    width= getOption("width") - 25   # you can make here your line shorter/longer
    pcur=0
    ret=curlPerform(url=url, writedata=f@ref,  noprogress=FALSE,
        progressfunction=function(down,up) pcur<<-progressDown(down, up, pcur, width),
        followlocation=T)
        close(f)
        cat('\n Download', names(ret), '- Ret', ret, '\n') # is success? 
}

用一个小样本二进制文件运行它:

curlProgress("http://www.nirsoft.net/utils/websitesniffer-x64.zip", "test.zip")

60%的中间输出是(没有#保护):

  |.................................                      | 133.74KB of 222.75KB  60%

其中 KB，将根据总大小调整为 B, KB, MB, GB。

成功状态的最终输出是:

  |.......................................................| 222.61KB of 222.75KB 100%
 Download OK - Ret 0 

请注意，输出线宽是相对于 R 宽度选项(它控制一行中的最大列数)并且可以通过更改 curlProgress 行进行自定义:

width= getOption("width") - 25

这足以满足我的需求并解决了我自己的问题。