feat(unitproc):Add checkTar. Makes sure a tar exists

Added checkTar() Bash function template. It checks to see if file arg1 is a
valid tar archive. If file exists but `tar` doesn't recognize it as
valid, then rename it with a nonce and create an empty tar in its place.

diff --git a/unitproc/bktemp-checkTar b/unitproc/bktemp-checkTar
new file mode 100644 (file)
index 0000000..2485f3a
--- /dev/null
+++ b/unitproc/bktemp-checkTar
@@ -0,0 +1,35 @@
+#!/bin/bash
+
+# Desc: Checks that a valid tar archive exists, creates one otherwise
+
+# Yell, Die, Try Three-Fingered Claw technique
+# Ref/Attrib: https://stackoverflow.com/a/25515370
+yell() { echo "$0: $*" >&2; }
+die() { yell "$*"; exit 111; }
+try() { "$@" || die "cannot $*"; }
+
+checkTar() {
+    # Desc: Checks that a valid tar archive exists, creates one otherwise
+    # Usage: checkTar [ path ]
+    # Input: arg1: path of tar archive
+    # Output: exit code 0: tar exists and is valid
+    # Depends: try, tar, date
+    local PATH_TAR="$1"
+
+    # Check if file is a valid tar archive
+    if tar --list --file="$PATH_TAR" 1>/dev/null 2>&1; then
+       ## T1: return success
+       return 0;
+    else
+       ## F1: Check if file exists
+       if [[ -f "$PATH_TAR" ]]; then
+           ### T: Rename file
+           try mv "$PATH_TAR" "$PATH_TAR""--broken--""$(date +%Y%m%dT%H%M%S)";
+       else
+           ### F: -
+           :
+       fi
+       ## F2: Create tar archive
+       try tar --create --file="$PATH_TAR" --files-from=/dev/null;
+    fi
+} # checks if arg1 is tar; creates one otherwise