3 files changed, 76 insertions, 0 deletions
diff --git a/README.markdown b/README.markdown
index 3e566177..66864981 100644
--- a/README.markdown
+++ b/README.markdown
@@ -443,6 +443,7 @@ Installed by the `install-bin` target:
 *   `maybe(1df)` is like `true(1)` or `false(1)`; given a probability of
     success,
     it exits with success or failure. Good for quick tests.
+*   `mex(1df)` makes given filenames in `$PATH` executable.
 *   `mftl(1df)` finds usable-looking targets in Makefiles.
 *   `mkcp(1df)` creates a directory and copies preceding arguments into it.
 *   `mkmv(1df)` creates a directory and moves preceding arguments into it.
diff --git a/bin/mex b/bin/mex
new file mode 100755
index 00000000..005149d8
--- /dev/null
+++ b/bin/mex
@@ -0,0 +1,53 @@
+#!/bin/sh
+# Make the first non-executable instance of files with the given names in $PATH
+# executable
+self=mex
+
+# Check we have at least one argument
+if [ "$#" -eq 0 ] ; then
+    printf >&2 '%s: At least one name required\n' "$self"
+    exit 2
+fi
+
+# Iterate through the given names
+for name ; do
+
+    # Clear the found variable
+    found=
+
+    # Start iterating through $PATH, with colon prefix/suffix to correctly
+    # handle the fenceposts
+    path=:$PATH:
+    while [ -n "$path" ] ; do
+
+        # Pop the first directory off $path into $dir
+        dir=${path%%:*}
+        path=${path#*:}
+
+        # Check $dir is non-null
+        [ -n "$dir" ] || continue
+
+        # If a file with the needed name exists in the directory and isn't
+        # executable, we've found our candidate and can stop iterating
+        if [ -f "$dir"/"$name" ] && ! [ -x "$dir"/"$name" ] ; then
+            found=$dir/$name
+            break
+        fi
+    done
+
+    # If the "found" variable was defined to something, we'll try to change its
+    # permissions
+    if [ -n "$found" ] ; then
+        chmod +x -- "$found" || ex=1
+
+    # If not, we'll report that we couldn't find it, and flag an error for the
+    # exit status
+    else
+        printf >&2 '%s: No non-executable name "%s" in PATH\n' "$self" "$name"
+        ex=1
+    fi
+done
+
+# We exit 1 if any of the names weren't found or if changing their permissions
+# failed
+exit "${ex:-0}"
diff --git a/man/man1/mex.1df b/man/man1/mex.1df
new file mode 100644
index 00000000..0fa584da
--- /dev/null
+++ b/man/man1/mex.1df
@@ -0,0 +1,22 @@
+.TH MEX 1df "September 2016" "Manual page for mex"
+.SH NAME
+.B mex
+\- make first instance of filenames in $PATH executable
+.SH USAGE
+.B mex
+name
+.br
+.B mex
+name1 name2 name3
+.br
+PATH=/foo:/bar/baz
+name
+.SH DESCRIPTION
+Iterate through the contents of the PATH variable looking for files with any of
+the specified names that do not have the executable permissions bit set, and
+try to set it if found. Exit nonzero if any of the names were not found, or if
+any of the permissions changes failed.
+.SH SEE ALSO
+chmod(1), eds(1df)
+.SH AUTHOR
+Tom Ryder <tom@sanctum.geek.nz>