> I can. I just want to know if the command is available for my script to > use; I don't care about the latest flamewar that moved it in or out of > /usr or */sbin.
You are searching for a particular word, and that word may represent a binary/script, a shell function, a shell alias, a shell builtin. There may be many of the aforementioned things with the same name. No mechanism exists to determine whether or not these things perform similar actions or have similar interfaces. Let's say that I want to run deathrampage in my postinst. deathrampage is a binary in a package of the same name, and this is the deathrampage that I wish to have executed. There are many ways for me to check for it: (A) deathrampage || echo uh-oh, continuing without it Advantages: portable Disadvantages: requires running the program in question (B) test -x /usr/sbin/deathrampage && /usr/sbin/deathrampage Advantages: portable, will not execute the wrong deathrampage unless someone has placed an impostor in /usr/sbin Disadvantages: will fail silently if deathrampage is moved to /usr/bin (C) multiple tests, or loop of tests Advantages: portable, will handle multiple finite locations Disadvantages: will fail silently if deathrampage is moved beyond the finite list of locations (D) command -v deathrampage 2>/dev/null && deathrampage OR type deathrampage 2>/dev/null && deathrampage Advantages: will find and execute deathrampage anywhere Disadvantages: will find and execute deathrampage anywhere, no matter if it is an alias to 'rm -rf /', a shell function that initiates immediate reboot, or some other bizarre and unexpected thing. Not POSIX-compliant. (E) which deathrampage 2>/dev/null && command deathrampage Advantages: will find and execute deathrampage on the command search path. Disadvantages: not standardized at all. builtin which's will not likely have the same interface. (F) /usr/bin/which deathrampage 2>/dev/null && command deathrampage Advantages: will find and execute deathrampage on the command search path. Disadvantages: requires faith in /usr/bin/which not moving or changing (G) dpkg -S deathrampage && some other stuff Advantages: will only find deathrampages tracked by the Debian packaging system. Disadvantages: slow and cumbersome (H) #!/bin/specific shell, and use known whence, which, type commands Advantages: no portability problems, and you might get exactly what you want Disadvantages: annoying to users everywhere (I) invent a Debian-specific solution to this problem Advantages: less confusion Disadvantages: requires cognition, and people seem to feel differently about whether or not they want random shell aliases, functions, and binaries in /usr/local being executed by package scripts. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
