regular expression in R with nth occurrence - regex

Question

I am reading a text file in R and want to replace every 3rd occurrence of '|' with '\n' here is my code and input data
**Input Data**
======================
'Monday, November 2, 2015|10:21:27|17:58:12|Tuesday, November 3, 2015|10:13:09|18:52:44|Wednesday, November 4, 2015|10:11:52|18:40:36|Thursday, November 5, 2015|10:31:42|18:16:57|Friday, November 6, 2015|10:13:13|--|Saturday, November 7, 2015|--|--|Sunday, November 8, 2015|--|--|Monday, November 9, 2015|--|--|Tuesday, November 10, 2015|10:03:20|18:07:52|Wednesday, November 11, 2015|09:40:20|18:42:20|Thursday, November 12, 2015|10:38:56|18:37:20|Friday, November 13, 2015|10:45:26|18:09:54|Saturday, November 14, 2015|--|--|Sunday, November 15, 2015|--|--|Monday, November 16, 2015|--|--|Tuesday, November 17, 2015|10:11:43|18:36:15|Wednesday, November 18, 2015|--|--|Thursday, November 19, 2015|--|--|Friday, November 20, 2015|12:14:25|20:25:08|Saturday, November 21, 2015|--|--|Sunday, November 22, 2015|--|--|Monday, November 23, 2015|10:08:08|17:57:35|Tuesday, November 24, 2015|14:30:32|--|'
**My R-Code**
====================
emp <- readChar(FileDir, (file.info(FileDir)$size-172))
emp <- gsub("\r\n","|",emp)
empTMP <- gsub('([^|]*|[^|]*|[^|]*)|',"\1\n",emp)
**output**
====================
"\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n|\001\n"
**Required output**
====================
Monday, November 2, 2015|10:21:27|17:58:12
Tuesday, November 3, 2015|10:13:09|18:52:44
Wednesday, November 4, 2015|10:11:52|18:40:36
Thursday, November 5, 2015|10:31:42|18:16:57
Friday, November 6, 2015|10:13:13|--
Saturday, November 7, 2015|--|--
Sunday, November 8, 2015|--|--
Monday, November 9, 2015|--|--
Tuesday, November 10, 2015|10:03:20|18:07:52
Wednesday, November 11, 2015|09:40:20|18:42:20
Thursday, November 12, 2015|10:38:56|18:37:20
Friday, November 13, 2015|10:45:26|18:09:54
Saturday, November 14, 2015|--|--
Sunday, November 15, 2015|--|--
Monday, November 16, 2015|--|--
Tuesday, November 17, 2015|10:11:43|18:36:15
Wednesday, November 18, 2015|--|--
Thursday, November 19, 2015|--|--
Friday, November 20, 2015|12:14:25|20:25:08
Saturday, November 21, 2015|--|--
Sunday, November 22, 2015|--|--
Monday, November 23, 2015|10:08:08|17:57:35
Tuesday, November 24, 2015|14:30:32|--
Kindly help what I am doing wrong, I check the above regular expression in text editor it works perfectly fine however in "R" it is not producing the correct result.

Answer 1

The following works:
#input <- #your input string
x <- strsplit(input, split = "|", fixed = TRUE)[[1L]]
idx <- seq(3L, length(x), by = 3L)
x[idx] <- paste0(x[idx], "\n")
x[-idx] <- paste0(x[-idx], "|")
paste(x, collapse = "")
Or in one command:
paste(paste0(x <- strsplit(input, split = "|", fixed = TRUE)[[1L]],
rep_len(c("|", "|", "\n"), length(x))), collapse = "")
And if you wanted to stick with gsub, this works as well:
gsub("([^|]*\\|[^|]*\\|[^|]*)\\|", "\\1\n", input)
Broken down (regex101 colored version):
gsub(paste0("(", #start capturing group 1
"[^|]*", #Matching anything but | 0 or more times
"\\|", #Match | (must escape because it's reserved for OR)
"[^|]*\\|", #again
"[^|]*", #again matching anything but |
")", #end captured group
"\\|"), #captured group is followed by a third |
"\\1\n",input) #replace match with captured group followed by \n
# (instead of |)
(just noticed your original attempt is very close. just that you forgot to escape things properly: "\\1", not "\1", and "|" is reserved so we have to escape that as well. Also #CAFEBABE is right that this seems better suited to awk...)

Answer 2

empTMP <- gsub('([^|]*|[^|]*|[^|]*)|',"\1\n",emp)
this is the line which causes imho the trouble.
It should be
empTMP <- gsub('([^|]*|[^|]*|[^|]*)|',"\\1\n",emp)
(note the \\1)
On the side: why do you want to use R for this task. Looks like something for standard shell scripting.
On the side 2: why teradata? On which TD box do you use R?