Something

steev@keuhi ~/repos/steev/sys-apps/hal $ bash -c 'a=/path/to/somedir;b=/path;c=${a##${b/}}'
bash: ${b/}: bad substitution
*** glibc detected *** bash: free(): invalid pointer: 0x1175da69 ***
======= Backtrace: =========
/lib/libc.so.6[0x55177ee2]
/lib/libc.so.6(cfree+0x87)[0x55179b97]
bash[0x116d7b64]
bash[0x116d8879]
bash[0x116d8a0d]
bash[0x116d8a5e]
bash[0x116d8b2a]
bash[0x116d496d]
bash[0x116d5e6d]
bash[0x116d6f81]
bash[0x116d8879]
bash(expand_string_assignment+0x82)[0x116d8d22]
bash[0x116d1524]
bash[0x116d1901]
bash[0x116d7f5e]
bash[0x116bd82c]
bash(execute_command_internal+0x687)[0x116bc0e7]
bash[0x116bb833]
bash(execute_command_internal+0xc4b)[0x116bc6ab]
bash(parse_and_execute+0x2a6)[0x116f4186]
bash[0x116a9dad]
bash(main+0xc0d)[0x116ab0ad]
/lib/libc.so.6(__libc_start_main+0xe0)[0x55128ff0]
bash[0x116a9191]
======= Memory map: ========
11690000-1173c000 r-xp 00000000 08:03 2389065    /bin/bash
1173c000-1173d000 r--p 000ab000 08:03 2389065    /bin/bash
1173d000-11743000 rw-p 000ac000 08:03 2389065    /bin/bash
11743000-11779000 rw-p 11743000 00:00 0          [heap]
54e00000-54e21000 rw-p 54e00000 00:00 0 
54e21000-54f00000 ---p 54e21000 00:00 0 
54f94000-54f9e000 r-xp 00000000 08:03 585841     /lib/libgcc_s.so.1
54f9e000-54f9f000 r--p 00009000 08:03 585841     /lib/libgcc_s.so.1
54f9f000-54fa0000 rw-p 0000a000 08:03 585841     /lib/libgcc_s.so.1
54fb0000-54ff2000 rw-p 54fb0000 00:00 0 
54ff2000-55031000 r--p 00000000 08:03 3541702    /usr/lib/locale/en_US.utf8/LC_CTYPE
55031000-55032000 r--p 00000000 08:03 3591652    /usr/lib/locale/en_US.utf8/LC_NUMERIC
55032000-55112000 r--p 00000000 08:03 3595074    /usr/lib/locale/en_US.utf8/LC_COLLATE
55112000-55113000 rw-p 55112000 00:00 0 
55113000-5523d000 r-xp 00000000 08:03 3665591    /lib/libc-2.6.1.so
5523d000-5523f000 r--p 0012a000 08:03 3665591    /lib/libc-2.6.1.so
5523f000-55240000 rw-p 0012c000 08:03 3665591    /lib/libc-2.6.1.so
55240000-55243000 rw-p 55240000 00:00 0 
55243000-55245000 r-xp 00000000 08:03 3665746    /lib/libdl-2.6.1.so
55245000-55246000 r--p 00001000 08:03 3665746    /lib/libdl-2.6.1.so
55246000-55247000 rw-p 00002000 08:03 3665746    /lib/libdl-2.6.1.so
55247000-55280000 r-xp 00000000 08:03 2289568    /lib/libncurses.so.5.6
55280000-55287000 r--p 00039000 08:03 2289568    /lib/libncurses.so.5.6
55287000-55289000 rw-p 00040000 08:03 2289568    /lib/libncurses.so.5.6
55289000-5528a000 rw-p 55289000 00:00 0 
5528a000-5528b000 r--p 00000000 08:03 3593048    /usr/lib/locale/en_US.utf8/LC_TIME
5528b000-5528c000 r--p 00000000 08:03 3595075    /usr/lib/locale/en_US.utf8/LC_MONETARY
5528c000-5528d000 r--p 00000000 08:03 3596090    /usr/lib/locale/en_US.utf8/LC_MESSAGES/SYS_LC_MESSAGES
5528d000-5528e000 r--p 00000000 08:03 3596096    /usr/lib/locale/en_US.utf8/LC_PAPER
5528e000-5528f000 r--p 00000000 08:03 3596097    /usr/lib/locale/en_US.utf8/LC_NAME
5528f000-55290000 r--p 00000000 08:03 3596099    /usr/lib/locale/en_US.utf8/LC_ADDRESS
55290000-55291000 r--p 00000000 08:03 3596101    /usr/lib/locale/en_US.utf8/LC_TELEPHONE
55291000-55292000 r--p 00000000 08:03 3596103    /usr/lib/locale/en_US.utf8/LC_MEASUREMENT
55292000-55299000 r--s 00000000 08:03 3392739    /usr/lib/gconv/gconv-modules.cache
55299000-5529a000 r--p 00000000 08:03 3596104    /usr/lib/locale/en_US.utf8/LC_IDENTIFICATION
5529a000-5529b000 r-xp 5529a000 00:00 0          [vdso]
5529b000-552b5000 r-xp 00000000 08:03 3665763    /lib/ld-2.6.1.so
552b5000-552b6000 r--p 00019000 08:03 3665763    /lib/ld-2.6.1.so
552b6000-552b7000 rw-p 0001a000 08:03 3665763    /lib/ld-2.6.1.so
5f3bd000-5f3d3000 rw-p bffea000 00:00 0          [stack]
71690000-7173c000 r-xp 00000000 08:03 2389065    /bin/bash
b4f94000-b4f9e000 r-xp 00000000 08:03 585841     /lib/libgcc_s.so.1
b5113000-b523d000 r-xp 00000000 08:03 3665591    /lib/libc-2.6.1.so
b5243000-b5245000 r-xp 00000000 08:03 3665746    /lib/libdl-2.6.1.so
b5247000-b5280000 r-xp 00000000 08:03 2289568    /lib/libncurses.so.5.6
b529a000-b529b000 r-xp 5529a000 00:00 0          [vdso]
b529b000-b52b5000 r-xp 00000000 08:03 3665763    /lib/ld-2.6.1.so
Aborted