cat: Concatenate and Print

Description Usage Arguments Details Value Note References See Also Examples


Outputs the objects, concatenating the representations. cat performs much less conversion than print.


cat(... , file = "", sep = " ", fill = FALSE, labels = NULL,
    append = FALSE)



R objects (see ‘Details’ for the types of objects allowed).


A connection, or a character string naming the file to print to. If "" (the default), cat prints to the standard output connection, the console unless redirected by sink. If it is "|cmd", the output is piped to the command given by ‘cmd’, by opening a pipe connection.


a character vector of strings to append after each element.


a logical or (positive) numeric controlling how the output is broken into successive lines. If FALSE (default), only newlines created explicitly by "\n" are printed. Otherwise, the output is broken into lines with print width equal to the option width if fill is TRUE, or the value of fill if this is numeric. Non-positive fill values are ignored, with a warning.


character vector of labels for the lines printed. Ignored if fill is FALSE.


logical. Only used if the argument file is the name of file (and not a connection or "|cmd"). If TRUE output will be appended to file; otherwise, it will overwrite the contents of file.


cat is useful for producing output in user-defined functions. It converts its arguments to character vectors, concatenates them to a single character vector, appends the given sep = string(s) to each element and then outputs them.

No linefeeds are output unless explicitly requested by "\n" or if generated by filling (if argument fill is TRUE or numeric).

If file is a connection and open for writing it is written from its current position. If it is not open, it is opened for the duration of the call in "wt" mode and then closed again.

Currently only atomic vectors and names are handled, together with NULL and other zero-length objects (which produce no output). Character strings are output ‘as is’ (unlike print.default which escapes non-printable characters and backslash — use encodeString if you want to output encoded strings using cat). Other types of R object should be converted (e.g., by as.character or format) before being passed to cat. That includes factors, which are output as integer vectors.

cat converts numeric/complex elements in the same way as print (and not in the same way as as.character which is used by the S equivalent), so options "digits" and "scipen" are relevant. However, it uses the minimum field width necessary for each element, rather than the same field width for all elements.


None (invisible NULL).


If any element of sep contains a newline character, it is treated as a vector of terminators rather than separators, an element being output after every vector element and a newline after the last. Entries are recycled as needed.


Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

See Also

print, format, and paste which concatenates into a string.


iter <- stats::rpois(1, lambda = 10)
## print an informative message
cat("iteration = ", iter <- iter + 1, "\n")

## 'fill' and label lines:
cat(paste(letters, 100* 1:26), fill = TRUE, labels = paste0("{", 1:10, "}:"))