Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
# Stephane Chazelas suggests the following alternative:
usage() {
echo "Usage: `basename $0` C−program−file" >&2
exit 1
}
WEIRD=`echo −n −e '\377'` # or WEIRD=$'\377'
[[ $# −eq 1 ]] || usage
case `file "$1"` in
*"C program text"*) sed −e "s%/\*%${WEIRD}%g;s%\*/%${WEIRD}%g" "$1" \
| tr '\377\n' '\n\377' \
| sed −ne 'p;n' \
| tr −d '\n' | tr '\377' '\n';;
*) usage;;
esac
# This is still fooled by things like:
# printf("/*");
# or
# /* /* buggy embedded comment */
#
# To handle all special cases (comments in strings, comments in string
# where there is a \", \\" ...) the only way is to write a C parser
# (lex or yacc perhaps?).
which
exit 0
which command−xxx gives the full path to "command−xxx". This is useful for finding out whether a
particular command or utility is installed on the system.
$bash which rm
/usr/bin/rm
whereis
Similar to which, above, whereis command−xxx gives the full path to "command−xxx", but also to
its manpage.
$bash whereis rm
whatis
rm: /bin/rm /usr/share/man/man1/rm.1.bz2
whatis filexxx looks up "filexxx" in the whatis database. This is useful for identifying system
commands and important configuration files. Consider it a simplified man command.
$bash whatis whatis
whatis
(1) − search the whatis database for complete words
Example 12−25. Exploring /usr/X11R6/bin
#!/bin/bash
# What are all those mysterious binaries in /usr/X11R6/bin?
Chapter 12. External Filters, Programs and Commands 181