feat(unitproc):Bash function to insert string into another string

diff --git a/unitproc/bkt-insertStr b/unitproc/bkt-insertStr
new file mode 100755 (executable)
index 0000000..6cea251
--- /dev/null
+++ b/unitproc/bkt-insertStr
@@ -0,0 +1,62 @@
+#!/usr/bin/env bash
+# Desc: Insert string into provided string
+
+yell() { echo "$0:${FUNCNAME[*]}: $*" >&2; }
+die() { yell "$*"; exit 111; }
+must() { "$@" || die "cannot $*"; }
+
+insertStr() {
+    # Desc: Inserts a
+    # Input: arg1: str   str_rec  String to receive insertion
+    #        arg2: int   pos      Insertion position (0 = append to front)
+    #        arg3: str   str_ins  String to be inserted
+    # Output: stdout:    Combined string
+    # Version: 0.0.1
+    # Depends: BK-2020-03: yell(), die(), must()
+    # Ref/Attrib: * BK-2020-03: https://gitlab.com/baltakatei/baltakatei-exdev/
+    
+    local str_rec pos str_ins;
+
+    # Check args
+    if [[ $# -ne 3 ]]; then
+        yell "ERROR:Invalid argument count:$#";
+        return 1; fi;
+    re='^[0-9]+$';
+    if [[ ! "$2" =~ $re ]]; then
+        yell "ERROR:Not an int:$2";
+        return 1; fi;
+    str_rec="$1";
+    pos="$2";
+    str_ins="$3";
+
+    # Calculate string stats
+    len_str_rec="${#str_rec}";
+    len_str_ins="${#str_ins}";
+
+    # Form prefix
+    pfx_pos_start="0";
+    pfx_len="$pos";
+    pfx="${str_rec:$pfx_pos_start:$pfx_len}";
+
+    # Form suffix
+    sfx_pos_start="$(( pos ))";
+    sfx_len="$(( len_str_rec - pos ))";
+    sfx="${str_rec:$sfx_pos_start:$sfx_len}";
+
+    # Print output to stdout
+    printf "%s%s%s\n" "$pfx" "$str_ins" "$sfx";    
+}; # Insert string provided at indicated position via stdout
+
+
+# Tests
+printf "\"%s\" should read \"foobarbaz\"\n" "$(insertStr "foobaz" 3 "bar";)";
+
+insertStr "foobaz" 0 "bar";
+insertStr "foobaz" 1 "bar";
+insertStr "foobaz" 2 "bar";
+insertStr "foobaz" 3 "bar";
+insertStr "foobaz" 4 "bar";
+insertStr "foobaz" 5 "bar";
+insertStr "foobaz" 6 "bar";
+insertStr "foobaz" 7 "bar";
+insertStr "foobaz" 999 "bar";