The shell utilities implement a number of shell commands you can use interactively or in shell scripts. Each utility program performs a specific task. The idea is that you can combine these commands in shell scripts to perform more complicated tasks.
Table 8-2 briefly describes each shell utility. You can try out some of these utilities by typing the program name at the shell prompt. Each program takes command-line options. You should first type man progname, where progname is the name of the utility, to learn more about the command-line options. Then try the utility with appropriate options.
Cross Ref |
You encounter some of these shell utilities again in Chapter 24 in the section covering shell programming. |
Program |
Description |
---|---|
[ |
Evaluates an expression and returns zero if the result is true (same as test) |
basename |
Removes the path prefix from a given pathname |
chroot |
Changes the root directory |
date |
Prints or sets the system date and time |
dirname |
Removes the last level or filename from a given pathname |
echo |
Prints a line of text |
env |
Prints environment variables or runs a command with modified environment variables |
expr |
Evaluates expressions |
factor |
Prints prime factors of a number |
false |
Returns an unsuccessful exit status |
groups |
Prints the names of the groups to which a user belongs |
hostid |
Prints the numeric identifier for the host |
id |
Prints the real and effective user and group IDs |
logname |
Prints the current login name |
nice |
Runs a program with specified scheduling priority |
nohup |
Allows a command to continue running after the user logs out |
pathchk |
Checks whether filenames are valid and portable |
pinky |
Prints information about users. (This is similar to the finger program; in fact, the name pinky refers to a lightweight finger.) |
printenv |
Prints environment variables |
printf |
Formats and prints data |
pwd |
Prints the working (current) directory |
seq |
Prints numeric sequences |
sleep |
Suspends execution for a specified time |
stty |
Prints or changes terminal settings |
su |
Enables the user to adopt the ID of another user, or the super user (root) |
tee |
Sends output to multiple files |
test |
Evaluates an expression and returns zero if the result is true |
true |
Returns a successful exit status |
tty |
Prints the terminal name |
uname |
Prints system information |
users |
Prints current user names |
who |
Prints a list of all users currently logged in |
whoami |
Prints the user name for the current effective user ID |
yes |
Prints a string repeatedly until the process is killed |