echo hi | cat - is also equivalent to echo hi | cat You only need the - if you are concatenating other files with stdin [1]. Incidentally, any use of

echo hi | cat - is also equivalent to echo hi | cat You only need the - if you are concatenating other files with stdin [1]. Incidentally, any use of echo x | y can be replaced (at least in Bash) with y <<< "x" This is called a "here string" [2]. [1] https://www.freebsd.org/cgi/man.cgi?query=cat&manpath=FreeBSD+9.1-RELEASE https://www.freebsd.org/cgi/man.cgi?query=cat&manpath=FreeBS... [2] http://tldp.org/LDP/abs/html/x17837.html http://tldp.org/LDP/abs/html/x17837.html