UNIX System Architecture and Shells

The software that controls the hardware resources of the computer is called the ______.

The shaded portion in the diagram represents the ______ that provides an interface to the kernel.

Applications can use both system calls and libraries of common ______.

The special application that provides an interface for running other applications is called the ______.

When logging in to a UNIX system, we enter our login name followed by our ______.

The file that stores user login information in UNIX systems is usually /etc/______.

In the password file entry, the numeric user ID is represented as ______.

Contemporary systems have moved the encrypted ______ to a different file.

The names in a directory are called ______.

The two characters that cannot appear in a filename are the slash character (/) and the ______.

A sequence of one or more filenames, separated by slashes, forms a ______.

A pathname that begins with a slash is called an ______.

Two special filenames created in every new directory are . (dot) and ______ (dot-dot).

The Research UNIX System restricted a filename to ______ characters.

For portability, POSIX.1 recommends that filenames consist of letters, numbers, period, dash, and ______.

A ______ pathname refers to files relative to the current directory.

The function ______ is used to read one line at a time from standard input.

The ______ character is often typed as Control-D to signal the end of input.

The program uses ______ to create a new process that is a copy of the caller.

In the child process, ______ is called to execute the command read from standard input.

To ensure that the command is executed correctly, the program replaces the newline character with a ______ byte.

The main process waits for the child process to finish using the ______ function.

If fgets returns a null pointer, the loop ______ and the process terminates.

To print the prompt, the program uses the ______ function.

The most common standard I/O function is ______.

The program uses the header ______ to include function prototypes for standard I/O functions.

The function ______ reads one character at a time from standard input.

The character read by getc is written using the function ______.

After the last byte of input is read, getc returns the constant ______.

An executing instance of a program is called a ______.

Every process has a unique numeric identifier called the ______.

The standard I/O constants stdin and stdout are defined in the ______ header.

The program created in the example demonstrates the functions ______ and perror.

When an error occurs, the program assigns the value ______ to errno to indicate 'No such file or directory'.

Using ______ allows us to know which program generated an error message in a pipeline.

In UNIX coding conventions, passing the program name to perror helps pinpoint the ______ that caused the error.

Fatal errors have no recovery actions and require printing an error message to the user or a ______.

System calls usually provide a minimal ______, whereas library functions often provide more elaborate functionality.

The process control system calls (fork, exec, and ______) are usually invoked by the user's application code directly.

Resource-related nonfatal errors include codes like EAGAIN, ENFILE, and ______.

The ______ library function is a common example that simplifies the invocation of system calls.

Shared resources being in use can lead to the ______ error being treated as nonfatal.

The typical recovery action for a resource-related nonfatal error is to delay and ______ later.

The ______ library function is often used as a programmer-friendly alternative to the sbrk system call.

In this text, we'll use the term ______ to refer to both system calls and library functions.

Each thread in a multithreaded environment requires a shared copy of errno to function correctly.

The value of errno can be both set to 0 and checked when a function indicates success.

The perror function outputs an error message based on the specified string and the current value of errno.

The function strerror(int *errnum) returns an error message string based on the value of a pointer to errnum.

In Linux, errno is defined as a simple global integer variable accessible by all threads.

The combination of fork followed by exec is called creating a new thread.

The waitpid function is used by the parent process to wait for the child process to finish.

Control-D is used to signify the start of input in UNIX systems.

To allow arguments in the program, input lines must be parsed to separate the arguments by spaces or tabs.

The child process uses execlp to execute a new program file.

The ls command can be executed with any specified directory using the current program.

Control characters in UNIX systems are formed by pressing the normal key combinations without the control key.

The termination status of the child process is ignored in the simple program mentioned.

A thread ID from one process is meaningful in another process.

Each thread in a process executes on its own stack.

The identifier errno is set to a positive value when an error occurs.

The open function returns -1 if an error occurs.

All functions in UNIX system return a pointer to an object to indicate an error.

Threads can access shared data without any need for synchronization.

The error constant EACCES indicates a permission problem.

Error constants in UNIX begin with the character Z.

A fatal error allows for recovery actions to be taken.

The error code ENOENT signifies 'No such file or directory'.

The perror function in C is used to print an error message associated with a specific error code.

Nonfatal errors can always be ignored without consequence.

Resource-related nonfatal errors can include temporary issues like resource shortage.

The statement 'EACCES: Permission denied' indicates a fatal error condition.

Using strerror, you can obtain a string message that describes the error corresponding to a specified error number.

The errno variable is used to keep track of error codes for all functions in C.

Ignoring a signal is recommended for hardware exceptions like dividing by zero.

The default action for a divide-by-zero condition is to terminate the process.

Catching a signal involves specifying a function to be executed when the signal occurs.

The quit key is typically the Control-C key.

A process can send a signal to another process only if it is the owner or the superuser.

The process terminates when the SIGINT signal is generated if it has not been set to handle it differently.

To generate a signal, one can only use keyboard interrupts.

The signal function is called to handle the SIGINT signal by printing a message.

The user ID assigned to a user can be changed by the user themselves.

Every user in a system has a user ID that is guaranteed to be unique.

The superuser or root user has limited permissions in the operating system.

Group IDs are used to collect users into groups for resource sharing.

Client versions of Mac OS X come with the superuser account enabled by default.

The group file in a system maps group names to numeric user IDs.

Exponential backoff algorithms involve waiting longer periods in each subsequent retry after an error.

The user ID of a user who logs in is presented in the system in decimal form.