'what' and 'mcs' in binutils?

Nisbach T., DP ITS, SCC, D Thomas.Nisbach@dp-itsolutions.de
Thu Jan 15 08:35:00 GMT 2004


Hi,

i am missing the tools 'what' and 'mcs'. Both are
common in the SysV world (e.g. Sun Solaris).

'what' searches an object/binary file for the SCCS
versioning tag '@(#)' and displays the string following.

'mcs' (manipulate comment section) can add/delete/...
arbitrary string to/from the '.comment' section of ELF.
This is useful to add any kind of release
information to an existing binary. 'what' lets you
display this information.

Details can be found on Solaris man pages:

what
====
http://docs.sun.com/db/doc/816-0210/6m6nb7mpv?a=view

mcs
====
http://docs.sun.com/db/doc/816-0210/6m6nb7men?a=view

My question:
=========
Is it intended to implement these commands?

I wrote two bash-scripts to emulate 'mcs -a ...'
and 'what' with the existing binutils tools.
'mcs' will be more complicated if applied to archives (libs).
In this case 'mcs' will be applied to any object-file
contained in the archive.

#!/bin/bash
# 
# Emulate 'mcs' (Manipulate Comment Section)
#
# Only 'mcs -a <string> <binary>' is supported.
# Archives (libs) ARE NOT SUPPORTET.
#
# Short description:
#   1) find the position of the '.comment'-section using 'objdump'
#   2) write out the raw '.comment'-section using 'dd'
#      (i am missing this option in objdump/objcopy)
#   3) replace (remove/add) the '.comment'-section using 'objcopy'
#
emu_mcs()
{
    if [ $# -eq  3 -a "$1" = "-a" ]; then
        string="$2"
        bin="$3"
        size=`objdump --section-headers "$bin" | fgrep .comment | awk '{ print $3 }'`
        offset=`objdump --section-headers "$bin" | fgrep .comment | awk '{ print $6 }'`
        if [ -n "$size" -a -n "$offset" ]; then
            # use bash hex-conversion
            size=$((0x$size))
            # skip=offset - 1
            skip=$((0x$offset - 1))
            # temporary file
            temp_comment=/tmp/emu_mcs_$$
            if [ $size -gt 0 ]; then
                dd if="$bin" of="$temp_comment" bs=1 skip=$skip count=$size 2>/dev/null
            fi
            echo "$string" >> "$temp_comment"
            objcopy --remove-section=.comment "$bin"
            objcopy --add-section .comment="$temp_comment" "$bin"
            rm -f "$temp_comment"
        fi
    else
        echo "Usage: emu_mcs -a <string> <binary>" >&2
        return 1
    fi
}

# Emulate 'what' (show SCCS version information)
emu_what()
{
    # scan all file sections (-a)
    strings -a "$1" | sed 's/\(@(#)\)/\n\1/g' | fgrep '@(#)' | cut -c 5-
}

Regards,

Thomas


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