title: readxl::read_xls returns "libxls error: Unable to open file"
body: <p>I have multiple .xls (~100MB) files from which I would like to load multiple sheets (from each) into R as a dataframe. I have tried various functions, such as <code>xlsx::xlsx2</code> and <code>XLConnect::readWorksheetFromFile</code>, both of which always run for a very long time (>15 mins) and never finish and I have to force-quit RStudio to keep working.</p>
  
  <p>I also tried <code>gdata::read.xls</code>, which does finish, but it takes more than 3 minutes per one sheet and it cannot extract multiple sheets at once (which would be very helpful to speed up my pipeline) like <code>XLConnect::loadWorkbook</code> can.</p>
  
  <p>The time it takes these functions to execute (and I am not even sure the first two would ever finish if I let them go longer) is way too long for my pipeline, where I need to work with many files at once. Is there a way to get these to go/finish faster?</p>
  
  <p>In several places, I have seen a recommendation to use the function <code>readxl::read_xls</code>, which seems to be widely recommended for this task and should be faster per sheet. This one, however, gives me an error:</p>
  
  <pre><code>&gt; # Minimal reproducible example:
  &gt; setwd("/Users/USER/Desktop")
  &gt; library(readxl)
  &gt; data &lt;- read_xls(path="test_file.xls")
  Error: 
    filepath: /Users/USER/Desktop/test_file.xls
    libxls error: Unable to open file
  </code></pre>
  
  <p>I also did some elementary testing to make sure the file exists and is in the correct format:</p>
  
  <pre><code>&gt; # Testing existence &amp; format of the file
  &gt; file.exists("test_file.xls")
  [1] TRUE
  &gt; format_from_ext("test_file.xls")
  [1] "xls"
  &gt; format_from_signature("test_file.xls")
  [1] "xls"
  </code></pre>
  
  <p>The <code>test_file.xls</code> used above is available <a href="https://drive.google.com/file/d/13NIs4fi6dHQ8eFKKycYCPjy89N29vln0/view?usp=sharing" rel="noreferrer">here</a>.
  Any advice would be appreciated in terms of making the first functions run faster or the <code>read_xls</code> run at all - thank you!</p>
  
  <h3>UPDATE:</h3>
  
  <p>It seems that some users are able to open the file above using the <code>readxl::read_xls</code> function, while others are not, both on Mac and Windows, using the most up to date versions of <code>R</code>, <code>Rstudio</code>, and <code>readxl</code>. The <a href="https://github.com/tidyverse/readxl/issues/598" rel="noreferrer">issue has been posted on the readxl GitHub</a> and has not been resolved yet.</p>