Michael Nelson writes:

Strangely enough though, "strace which ls" reports:

old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x40016000 write(1, "/bin/ls\n", 8/bin/ls ) = 8 munmap(0x40016000, 4096) = 0 _exit(0)

...but it doesn't get written to the screen:

seahunt:~$ which ls seahunt:~$

Note that strace invokes /usr/bin/which and it reports /bin/ls on the stdout: $ strace which ls 2>/dev/null /bin/ls The following is from bash(1): : Aliases allow a string to be substituted for a word when : it is used as the first word of a simple command. In "strace which ls" the "which" is the second word and therefore it's not interpreted as an alias while in "which ls" it is an alias. -- Alexandr.Malusek@imv.liu.se