Suppress system error with trycatch in R - r

Question

I am unable to supress the error,though my pdf file is getting converted into text but i am unable to suppress this error.
tryCatch(system(paste("\"", exe, "\" \"", dest, "\"", sep = ""), wait = T))
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
> suppressWarnings(system(paste("\"", exe, "\" \"", dest, "\"", sep = ""), wait = T))
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
>tryCatch(system(paste("\"", exe, "\" \"", dest, "\"", sep = ""), wait = T), error = function(e) e)
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
> suppressMessages(system(paste("\"", exe, "\" \"", dest, "\"", sep = ""), wait = T))
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
> tryCatch(suppressWarnings(capture.output(system(paste("\"", exe, "\" \"", dest, "\"", sep = ""), wait = T))), error = function(e) e)
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
character(0)
> tryCatch({system(paste("\"", exe, "\" \"", dest, "\"", sep = ""), wait = T)}, error = function(e) e)
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Any reason why am i unable to suppress it ? how can i get rid of this error ?Thanks.
EDIT
With silent=TRUE and function(e){invisible(e)}
tryCatch(system(paste("\"", exe, "\" \"", dest, "\"", sep = ""), wait = T), error = function(e){invisible(e)})
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
> try(system(paste("\"", exe, "\" \"", dest, "\"", sep = ""), wait = T),silent=TRUE)
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
Syntax Error: Missing or invalid 'Bounds' entry in stitching function
EDITED
It stopped the error but it has also stopped the functionality as well,The pdf file is not getting converted into text by this.
tryCatch(system2(paste("\"", exe, "\" \"", dest, "\"", sep = ""), wait = TRUE,
stdout=TRUE, stderr=TRUE),
error=function(err) NA)
[1] NA
source code
dest=paste("C:/wamp/www/LU/my/pdffiles",file_list[i],sep="/")
exe <- "C:\\Program Files\\xpdfbin-win-3.03\\bin32\\pdftotext.exe"
try(system(paste("\"", exe, "\" \"", dest, "\"", sep = ""), wait = TRUE),
silent=TRUE)

Answer 1

Normally one would write
tryCatch({
system("xyz")
}, error=function(err) {
## do something with 'err', then maybe throw it again stop(err)
## or providing an alternative return value
NA
})
So
> xx = tryCatch(stop("oops"), error=function(err) NA)
> xx
[1] NA
but it seems that some errors thrown by system() cannot be caught in this way.
> xx = tryCatch(system("foobar"), error=function(err) NA)
sh: 1: foobar: not found
The hint that something might be done is from the value of xx:
> xx
[1] 127
The help page first points us to system2() instead, where we see
If 'stdout = TRUE' or 'stderr = TRUE', a character vector giving
the output of the command, one line per character string. (Output
lines of more than 8095 bytes will be split.) If the command
could not be run an R error is generated.
and sure enough
> tryCatch(system2("foobar", stdout=TRUE, stderr=TRUE), error=function(err) NA)
[1] NA

Answer 2

Never actually used tryCatch() before but it seems your error function is error=function(e) e so you are just returning the error you get.
I have used try() in the past with option silent=TRUE to avoid showing the error message. Something like this (disclaimer, the help page for try mentions that using tryCatch may be more efficient):
res=try(runif(Inf), silent=TRUE)
if(class(res)=="try-error") {
print("some error happened")
} else {
print(res)
}
res=try(runif(10), silent=TRUE)
if(class(res)=="try-error") {
print("some error happened")
} else {
print(res)
}
There may be better ways to do this and hopefully others will correct my solution.