Break REST for site redirects

My position: I have a long (20k lines) list of URLs that I need to clean up individual data items for analysis. For the purposes of this example, I'm looking for a specific field called "sol-num" that is the invitation number. Using the following function, I can get the invitation number for any purchases listed in FedBizOpps:

require(rvest)
require(magrittr)
fetchSolNum<-function(URL){
  URL<-as.character(URL)
  solNum<-html(URL)%>%
    html_node(".sol-num")%>%
    html_text()
}

      

        
        
        
      

    

Now I have a list of thousands of URLs and I want to pull the request number for each one by entering it in a new column in the dataframe from which I got the list of URLs. For your own testing, here are the first ten lines in the list of URLs:

list<-c("https://www.fbo.gov/spg/DISA/D4AD/DITCO/HC1028-12-T-0025/listing.html",
"https://www.fbo.gov/notices/c360b067077aabde331d66e0fe2d1f8f",         
"https://www.fbo.gov/notices/f63053a7a6e858a5b7b537a660c473b7",         
"https://www.fbo.gov/spg/DLA/J3/DSCP-I/SPM300-12-R-0024/listing.html",  
"https://www.fbo.gov/spg/DLA/J3/DAPS/SP7000-11-Q-0047/listing.html",    
"https://www.fbo.gov/spg/USAF/AFMC/OCALCCC/F3YCDW1245A001/listing.html",
"https://www.fbo.gov/spg/USAF/AFMC/AFFTC/FA9300-12-R-5001/listing.html",
"https://www.fbo.gov/notices/17ddec6ae37feb69704b1a52e22eeb26",         
"https://www.fbo.gov/notices/3b76d40705a23a749aad46df88dcee0c",         
"https://www.fbo.gov/notices/91873b727968dc664ada76c48e53e4df") 
raw <- data.frame(matrix(unlist(list), nrow=10, byrow=T))

      

        
        
        
      

    

I want to store the output in a variable solNum

in my named dataframe raw

, so my function should have used a loop right now:

raw$solNum<-0

j=1
for (i in list){
  raw$solNum[j]<-fetchSolNum(i)
  j=j+1
}   

      

        
        
        
      

    

Running the code is currently deferring the values ​​for the top five lines and then returning the following error:

 Error in xml_apply(x, XML::xmlValue, ..., .type = character(1)) : 
  Unknown input of class: NULL 

      

        
        
        
      

    

After further investigation I found out that the problem is probably that this URL is from the list: https://www.fbo.gov/spg/USAF/AFMC/OCALCCC/F3YCDW1245A001/listing.html goes to this kind of page with ambiguous values ​​as there are two deals with this URL.

Considering my full list is 20k lines long, I don't have time to go through and clear the list of all invalid URLs. Is there a way for my current function to just insert the NA value for strings where the url is invalid or something? How can I get it not to break this error?

Also, reading around tells me that it might be faster and more efficient to perform this operation as a vectorized function rather than a loop. Can anyone give any advice on what might look like in my case?