/regexp/replacement/

Attempt to match regexp against the pattern space. If successful, replace that portion matched with replacement. The replacement may contain the special character & to refer to that portion of the pattern space which matched, and the special escapes \1 through \9 to refer to the corresponding matching sub-expressions in the regexp.

dell:~/Linux_Docs/tldp.org_guide$ ls *.tar.gz

Bash-Beginners-Guide.html.tar.gz Win+OpenSolaris+CentOS-Install.html.tar.gz
Bugzilla-Guide.html.tar.gz abs-guide.html.tar.gz
EVMSUG.html.tar.gz intro-linux.html.tar.gz
GNU-Linux-Tools-Summary.html.tar.gz lame.html.tar.gz
LDP-Author-Guide.html.tar.gz lki.html.tar.gz
Linux-Dictionary.html.tar.gz lkmpg.html.tar.gz
Linux-Filesystem-Hierarchy.html.tar.gz nag-2.0.html.tar.gz
Linux-Media-Guide.html.tar.gz sag.html.tar.gz
Mobile-Guide.html.tar.gz tlk.html.tar.gz
Pocket-Linux-Guide.html.tar.gz

dell:~/Linux_Docs/tldp.org_guide$ ls *.tar.gz | sed s/.tar.gz//

Bash-Beginners-Guide.html
Bugzilla-Guide.html
EVMSUG.html
GNU-Linux-Tools-Summary.html
LDP-Author-Guide.html
Linux-Dictionary.html
Linux-Filesystem-Hierarchy.html
Linux-Media-Guide.html
Mobile-Guide.html
Pocket-Linux-Guide.html
Win+OpenSolaris+CentOS-Install.html
abs-guide.html
intro-linux.html
lame.html
lki.html
lkmpg.html
nag-2.0.html
sag.html
tlk.html