25.11 crush: A cat that Skips all Blank Lines

Sometimes I have a series of files, or just one file, with lots of blank lines. Some systems have a -s option to cat that causes it to compress adjacent blank lines into one. If that option isn't available, you can use crush . The crush script skips all lines that are empty or have only blanks and/or TABs. Here it is:

#!/bin/sed -f /^[    ]*$/d

The brackets, [ ] , have a TAB and a space in them. That file doesn't even use a shell, so it's efficient; the kernel starts sed directly ( 45.3 ) and gives it the script itself as the input file expected with the -f option. If your UNIX can't execute files directly with #! , type in this version instead:

exec sed '/^[    ]*$/d' ${1+"$@"}

It starts a shell, then exec replaces the shell with sed ( 45.7 ) . The ${1+"$@"} works around a problem with argument handling ( 46.7 ) in some Bourne shells.