efrecon · February 8, 2024 13:19 · May 27, 2020 · May 27, 2020 · May 27, 2020 · May 25, 2020
diff --git a/docker_tags.md b/docker_tags.md
@@ -1,6 +1,6 @@
 # Docker Tags
 
-:no_entry: [DEPRECATED] Active as a real [project] instead, development as a
+:no_entry: **[DEPRECATED]** Active as a real [project] instead, development as a
 gist has been discontinued.
 
   [project]: https://github.com/efrecon/reg-tags

diff --git a/docker_tags.md b/docker_tags.md
@@ -1,6 +1,6 @@
 # Docker Tags
 
-**NOTE** This gist has moved to a real [project] instead, development as a
+:no_entry: [DEPRECATED] Active as a real [project] instead, development as a
 gist has been discontinued.
 
   [project]: https://github.com/efrecon/reg-tags

diff --git a/docker_tags.md → docker_tags.md b/docker_tags.md → docker_tags.md
@@ -1,5 +1,10 @@
 # Docker Tags
 
+**NOTE** This gist has moved to a real [project] instead, development as a
+gist has been discontinued.
+
+  [project]: https://github.com/efrecon/reg-tags
+
 This "script" implements a single function to list the existing tags at the
 Docker [hub] for a given public image.
 

diff --git a/docker_tags.sh b/docker_tags.sh
@@ -1,13 +1,17 @@
 #!/usr/bin/env sh
 
 docker_tags() {
-    filter=.*
+    _filter=".*"
+    _verbose=0
     while [ $# -gt 0 ]; do
         case "$1" in
             -f | --filter)
-                filter=$2; shift 2;;
+                _filter=$2; shift 2;;
             --filter=*)
-                filter="${1#*=}"; shift 1;;
+                _filter="${1#*=}"; shift 1;;
+
+            -v | --verbose)
+                _verbose=1; shift;;
 
             --)
                 shift; break;;
@@ -18,42 +22,53 @@ docker_tags() {
         esac
     done
 
-
-    if printf %s\\n "$1" | grep -oq '/'; then
-        hub="https://registry.hub.docker.com/v2/repositories/$1/tags/"
-    else
-        hub="https://registry.hub.docker.com/v2/repositories/library/$1/tags/"
-    fi
-
-    # Get number of pages
+    # Decide how to download silently
     download=
     if command -v curl >/dev/null; then
+        [ "$_verbose" = "1" ] && echo "Using curl for downloads" >&2
         # shellcheck disable=SC2037
         download="curl -sSL"
     elif command -v wget >/dev/null; then
+        [ "$_verbose" = "1" ] && echo "Using wget for downloads" >&2
         # shellcheck disable=SC2037
         download="wget -q -O -"
     else
         return 1
     fi
 
+    # Library images or user/org images?
+    if printf %s\\n "$1" | grep -oq '/'; then
+        hub="https://registry.hub.docker.com/v2/repositories/$1/tags/"
+    else
+        hub="https://registry.hub.docker.com/v2/repositories/library/$1/tags/"
+    fi
+    [ "$_verbose" = "1" ] && echo "Discovering pagination from $hub" >&2
+
+    # Get number of pages
     first=$($download "$hub")
     count=$(printf %s\\n "$first" | sed -E 's/\{\s*"count":\s*([0-9]+).*/\1/')
-    [ "$count" = "0" ] && return 0
+    if [ "$count" = "0" ]; then
+        [ "$_verbose" = "1" ] && echo "No tags, probably non-existing repo" >&2
+        return 0
+    else
+        [ "$_verbose" = "1" ] && echo "$count existing tag(s) for $1" >&2
+    fi
     pagination=$(   printf %s\\n "$first" |
                     grep -Eo '"name":\s*"[a-zA-Z0-9_.-]+"' |
                     wc -l)
     pages=$(( count / pagination + 1))
+    [ "$_verbose" = "1" ] && echo "$pages pages to download for $1" >&2
 
     # Get all tags one page after the other
     i=0
-    while [ "$i" -le "$pages" ]; do
+    while [ "$i" -lt "$pages" ]; do
         i=$(( i + 1 ))
+        [ "$_verbose" = "1" ] && echo "Downloading page $i / $pages" >&2
         page=$($download "$hub?page=$i")
         printf %s\\n "$page" |
             grep -Eo '"name":\s*"[a-zA-Z0-9_.-]+"' |
             sed -E 's/"name":\s*"([a-zA-Z0-9_.-]+)"/\1/' |
-            grep -E "$filter"
+            grep -E "$_filter"
     done
 }
 

diff --git a/docker_tags.md b/docker_tags.md
@@ -0,0 +1,34 @@
+# Docker Tags
+
+This "script" implements a single function to list the existing tags at the
+Docker [hub] for a given public image.
+
+  [hub]: https://hub.docker.com/
+
+When called as a script, all arguments will be forwarded to the function so that
+you will be able to try it.
+
+## Synopsis
+
+The function takes short options led by a single-dash, or long options led by a
+double dash. Long options can be separated from their value by an equal sign or
+a space separator. Recognised options are:
+
++ `-f` or `--filter`, a regular expression to restrict tags to versions matching
+  the expression.
+
+## Example
+
+The following will return all tags for the official [alpine] image:
+
+```shell
+./docker_tags.sh alpine
+```
+
+The following would only return "real" releases for [alpine]:
+
+```shell
+./docker_tags.sh --filter '[0-9]+(\.[0-9]+)+' alpine
+```
+
+  [alpine]: https://hub.docker.com/_/alpine
diff --git a/docker_tags.sh b/docker_tags.sh
@@ -57,6 +57,7 @@ docker_tags() {
     done
 }
 
-if [ "$#" -gt "0" ]; then
+# Run directly? call function!
+if [ "$(basename "$0")" = "docker_tags.sh" ] && [ "$#" -gt "0" ]; then
     docker_tags "$@"
 fi
diff --git a/docker_tags.sh b/docker_tags.sh
@@ -0,0 +1,62 @@
+#!/usr/bin/env sh
+
+docker_tags() {
+    filter=.*
+    while [ $# -gt 0 ]; do
+        case "$1" in
+            -f | --filter)
+                filter=$2; shift 2;;
+            --filter=*)
+                filter="${1#*=}"; shift 1;;
+
+            --)
+                shift; break;;
+            -*)
+                echo "$1 unknown option!" >&2; return 1;;
+            *)
+                break;
+        esac
+    done
+
+
+    if printf %s\\n "$1" | grep -oq '/'; then
+        hub="https://registry.hub.docker.com/v2/repositories/$1/tags/"
+    else
+        hub="https://registry.hub.docker.com/v2/repositories/library/$1/tags/"
+    fi
+
+    # Get number of pages
+    download=
+    if command -v curl >/dev/null; then
+        # shellcheck disable=SC2037
+        download="curl -sSL"
+    elif command -v wget >/dev/null; then
+        # shellcheck disable=SC2037
+        download="wget -q -O -"
+    else
+        return 1
+    fi
+
+    first=$($download "$hub")
+    count=$(printf %s\\n "$first" | sed -E 's/\{\s*"count":\s*([0-9]+).*/\1/')
+    [ "$count" = "0" ] && return 0
+    pagination=$(   printf %s\\n "$first" |
+                    grep -Eo '"name":\s*"[a-zA-Z0-9_.-]+"' |
+                    wc -l)
+    pages=$(( count / pagination + 1))
+
+    # Get all tags one page after the other
+    i=0
+    while [ "$i" -le "$pages" ]; do
+        i=$(( i + 1 ))
+        page=$($download "$hub?page=$i")
+        printf %s\\n "$page" |
+            grep -Eo '"name":\s*"[a-zA-Z0-9_.-]+"' |
+            sed -E 's/"name":\s*"([a-zA-Z0-9_.-]+)"/\1/' |
+            grep -E "$filter"
+    done
+}
+
+if [ "$#" -gt "0" ]; then
+    docker_tags "$@"
+fi