Chapter 4

LINUX Shells

Table 4.1  Shell Locations and Program Names

Figure 4.1 Shell families and their relative functionalities

Table 4.2 Shell Similarities and Disimilarities

Table 4.2 Shell Similarities and Disimilarities (continued from previous slide)

Table 4.3 Some Useful Shell Built-In Commands

Table 4.4 Shell Environment Variables

Table 4.5 Shell Startup Files for Bash and TC Shells

Shell Startup Files

• Startup files set environment variables and set the initial behavior of the shell

• Bash first runs the file /etc/profile• Additional startup files have names that start

with “.” which denotes a hidden file

Figure 4.2  An illustration of the write command (continued on next slide)

Figure 4.2  An illustration of the write command (continued from previous slide

Table 4.6 Some Useful Aliases

Some Useful Commands

• Directory commands: pwd, mkdir, rmdir, ls• File display commands: cat, more, less• File printing: lpr• Calendar display: cal• Instant Messaging: write, talk (can be enabled or disabled

using mesg)• Email notification: enabled or disabled using biff• Aliasing: create an alias name for long commands (alias, and

unalias)• System statistics: uptime, ps

Shell Metacharacters

• Metacharacters are characters that have a special meaning to the shell

• Metacharacters can be used as regular characters by preceding them with “\”

Table 4.7 Shell Metacharacters (continued on next slide)

Table 4.7 Shell Metacharacters (continued from

previous slide)