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+# ===================================================================== #
+#  An R package by Certe:                                               #
+#  https://github.com/certe-medical-epidemiology                        #
+#                                                                       #
+#  Licensed as GPL-v2.0.                                                #
+#                                                                       #
+#  Developed at non-profit organisation Certe Medical Diagnostics &     #
+#  Advice, department of Medical Epidemiology.                          #
+#                                                                       #
+#  This R package is free software; you can freely use and distribute   #
+#  it for both personal and commercial purposes under the terms of the  #
+#  GNU General Public License version 2.0 (GNU GPL-2), as published by  #
+#  the Free Software Foundation.                                        #
+#                                                                       #
+#  We created this package for both routine data analysis and academic  #
+#  research and it was publicly released in the hope that it will be    #
+#  useful, but it comes WITHOUT ANY WARRANTY OR LIABILITY.              #
+# ===================================================================== #
+
+# These functions are universal; they are internal functions in every Certe R package.
+# This is to prevent dependency on one another.
+# They are also exported in the 'certetoolbox' package.
+
+like <- function (x, pattern) {
+  x <- tolower(x)
+  pattern <- tolower(pattern)
+  if (length(pattern) == 1) {
+    # only one pattern
+    grepl(pattern, x, ignore.case = FALSE, fixed = FALSE,  perl = TRUE)
+  } else {
+    # multiple patterns
+    if (length(x) == 1) {
+      x <- rep(x, length(pattern))
+    } else {
+      stop("'x' and 'pattern' must be of equal length", call. = FALSE)
+    }
+    unlist(mapply(FUN = grepl, x = x, pattern = pattern, 
+                  fixed = FALSE, perl = TRUE, MoreArgs = list(ignore.case = FALSE), 
+                  SIMPLIFY = FALSE, USE.NAMES = FALSE))
+  }
+}
+`%like%` <- function(x, pattern) {
+  like(x = x, pattern = pattern)
+}
+`%unlike%` <- function(x, pattern) {
+  !like(x = x, pattern = pattern)
+}
+concat <- function(...) {
+  paste(c(...), collapse = "", sep = "")
+}
+#' @importFrom yaml read_yaml
+read_secret <- function(property, file = Sys.getenv("secrets_file")) {
+  if (file == "" && identical(file, Sys.getenv("secrets_file"))) {
+    warning("In read_secret(): environmental variable 'secrets_file' not set", call. = FALSE)
+    return("")
+  }
+  contents <- read_yaml(file)
+  if (!property %in% names(contents)) {
+    warning("In read_secret(): property '", property, "' not found", call. = FALSE)
+    return("")
+  }
+  contents[[property]]
+}