isomorphismes

(also known as C:\progra~1 in older Windowses)

Short answer: /bin or /usr/bin.

Longer answer: It depends on the distro (Ubuntu, Slack, Arch, Mint, Puppy, etc) and on what kind of program. You could think of these directories as decreasing from user land toward the bare-metal computer level. (Roughly / sort-of / not exactly.)

• /opt/ (programs you download)

• /bin/ (netstat, uname, wc, zcat, rm, rmdir, gzip, head, tail, last, ln, ls, kill, gawk, sleep, sort, tar, touch, vi, cat, chmod, sh, bzip2, bash, dmesg)
• /usr/bin/ (lpr, xsane, zipgrep, xrandr, xsane, less, leafpad, ldd, xinit, dpkg, ssh, sudo, sftp, dvipdf, evince)
• /usr/sbin/ (gtkdialog, parted, wpa_supplicant, ethtool, nscd, grub, dhcpd, httpd, cupsd, alsaconf)
• /sbin/ ( fsck, fdisk, mount, swapon, ifup, sysctl, lspci)

You should preferably store programs you download in:

• /opt/.

(for optional) and add /opt/ or /opt/bin/ to your $PATH with

• echo $PATH
• export PATH=$PATH:/opt
• echo $PATH

(if that gives you an error you may need to give yourself access with chown or chmod. For example chown isomorphismes /opt/ or chmod -R a+rw /opt/.

If you want to find where some command or program you use is located, use which.

# which ls
/bin/ls

# which grep
/bin/grep

# which top
/usr/bin/top

# which java
/usr/bin/java

# which ghci

# which ruby
/usr/bin/ruby

# which python
/usr/bin/python

# which perl
/usr/bin/perl

# which jwm
/usr/bin/jwm

# which awesomewm

# which xinit
/usr/bin/xinit

# which latex
/usr/bin/latex

# which pdflatex
/usr/bin/pdflatex

# which dvips
/usr/bin/dvips

# which sage

# which ack-grep
/usr/bin/ack-grep

# which ack

# which gdb
/usr/bin/gdb

# which epdfview
/usr/bin/epdfiew

# which dpaste
/opt/dpaste

# which lein
/opt/lein

# which less
/usr/bin/less