LIBSTAND(3) BSD Library Functions Manual LIBSTAND(3)
libstand -- support library for standalone executables
The libstand library provides a set of supporting functions for standalone applications, mimicking where possible the standard BSD program-
ming environment. The following sections group these functions by kind. Unless specifically described here, see the corresponding section 3
manpages for the given functions.
String functions are available as documented in string(3) and bstring(3).
void * malloc(size_t size)
Allocate size bytes of memory from the heap using a best-fit algorithm.
void free(void *ptr)
Free the allocated object at ptr.
void setheap(void *start, void *limit)
Initialise the heap. This function must be called before calling alloc() for the first time. The region between start and limit
will be used for the heap; attempting to allocate beyond this will result in a panic.
char * sbrk(int junk)
Provides the behaviour of sbrk(0), i.e., returns the highest point that the heap has reached. This value can be used during
testing to determine the actual heap usage. The junk argument is ignored.
A set of functions are provided for manipulating a flat variable space similar to the traditional shell-supported environment. Major
enhancements are support for set/unset hook functions.
char * getenv(const char *name)
int setenv(const char *name, const char *value, int overwrite)
int putenv(const char *string)
int unsetenv(const char *name)
These functions behave similarly to their standard library counterparts.
struct env_var * env_getenv(const char *name)
Looks up a variable in the environment and returns its entire data structure.
int env_setenv(const char *name, int flags, const void *value, ev_sethook_t sethook, ev_unsethook_t unsethook)
Creates a new or sets an existing environment variable called name. If creating a new variable, the sethook and unsethook argu-
ments may be specified.
The set hook is invoked whenever an attempt is made to set the variable, unless the EV_NOHOOK flag is set. Typically a set hook
will validate the value argument, and then call env_setenv() again with EV_NOHOOK set to actually save the value. The predefined
function env_noset() may be specified to refuse all attempts to set a variable.
The unset hook is invoked when an attempt is made to unset a variable. If it returns zero, the variable will be unset. The pre-
defined function env_nounset may be used to prevent a variable being unset.
STANDARD LIBRARY SUPPORT
int getopt(int argc, char * const *argv, const char *optstring)
long strtol(const char *nptr, char **endptr, int base)
void srandom(unsigned long seed)
unsigned long random(void)
char * strerror(int error)
Returns error messages for the subset of errno values supported by libstand.
int setjmp(jmp_buf env)
void longjmp(jmp_buf env, int val)
Defined as _setjmp() and _longjmp() respectively as there is no signal state to manipulate. Requires <setjmp.h>.
void gets(char *buf)
Read characters from the console into buf. All of the standard cautions apply to this function.
void ngets(char *buf, int size)
Read at most size - 1 characters from the console into buf. If size is less than 1, the function's behaviour is as for gets().
int fgetstr(char *buf, int size, int fd)
Read a line of at most size characters into buf. Line terminating characters are stripped, and the buffer is always NUL termi-
nated. Returns the number of characters in buf if successful, or -1 if a read error occurs.
int printf(const char *fmt, ...)
void vprintf(const char *fmt, va_list ap)
int sprintf(char *buf, const char *fmt, ...)
void vsprintf(char *buf, const char *fmt, va_list ap)
The *printf functions implement a subset of the standard printf() family functionality and some extensions. The following stan-
dard conversions are supported: c,d,n,o,p,s,u,x. The following modifiers are supported: +,-,#,*,0,field width,precision,l.
The b conversion is provided to decode error registers. Its usage is:
printf( "reg=%b\n", regval, "<base><arg>*" );
where <base> is the output expressed as a control character, e.g. \10 gives octal, \20 gives hex. Each <arg> is a sequence of
characters, the first of which gives the bit number to be inspected (origin 1) and the next characters (up to a character less
than 32) give the text to be displayed if the bit is set. Thus
printf( "reg=%b\n", 3, "\10\2BITTWO\1BITONE" );
would give the output
The D conversion provides a hexdump facility, e.g.
printf( "%6D", ptr, ":" ); gives "XX:XX:XX:XX:XX:XX"
printf( "%*D", len, ptr, " " ); gives "XX XX XX ..."
CHARACTER TESTS AND CONVERSIONS
int isupper(int c)
int islower(int c)
int isspace(int c)
int isdigit(int c)
int isxdigit(int c)
int isascii(int c)
int isalpha(int c)
int toupper(int c)
int tolower(int c)
int open(const char *path, int flags)
Similar to the behaviour as specified in open(2), except that file creation is not supported, so the mode parameter is not
required. The flags argument may be one of O_RDONLY, O_WRONLY and O_RDWR (although no file systems currently support writing).
int close(int fd)
Close all open files.
ssize_t read(int fd, void *buf, size_t len)
ssize_t write(int fd, void *buf, size_t len)
(No file systems currently support writing.)
off_t lseek(int fd, off_t offset, int whence)
Files being automatically uncompressed during reading cannot seek backwards from the current point.
int stat(const char *path, struct stat *sb)
int fstat(int fd, struct stat *sb)
The stat() and fstat() functions only fill out the following fields in the sb structure: st_mode,st_nlink,st_uid,st_gid,st_size.
The tftp file system cannot provide meaningful values for this call, and the cd9660 file system always reports files having
uid/gid of zero.
The libstand library supplies a simple internal pager to ease reading the output of large commands.
Initialises the pager and tells it that the next line output will be the top of the display. The environment variable LINES is
consulted to determine the number of lines to be displayed before pausing.
Closes the pager.
int pager_output(const char *lines)
Sends the lines in the NUL-terminated buffer at lines to the pager. Newline characters are counted in order to determine the
number of lines being output (wrapped lines are not accounted for). The pager_output() function will return zero when all of the
lines have been output, or nonzero if the display was paused and the user elected to quit.
int pager_file(const char *fname)
Attempts to open and display the file fname. Returns -1 on error, 0 at EOF, or 1 if the user elects to quit while reading.
Successive calls emit the characters in the sequence |,/,-,\ followed by a backspace in order to provide reassurance to the user.
REQUIRED LOW-LEVEL SUPPORT
The following resources are consumed by libstand - stack, heap, console and devices.
The stack must be established before libstand functions can be invoked. Stack requirements vary depending on the functions and file systems
used by the consumer and the support layer functions detailed below.
The heap must be established before calling alloc() or open() by calling setheap(). Heap usage will vary depending on the number of simulta-
neously open files, as well as client behaviour. Automatic decompression will allocate more than 64K of data per open file.
Console access is performed via the getchar(), putchar() and ischar() functions detailed below.
Device access is initiated via devopen() and is performed through the dv_strategy(), dv_ioctl() and dv_close() functions in the device switch
structure that devopen() returns.
The consumer must provide the following support functions:
Return a character from the console, used by gets(), ngets() and pager functions.
Returns nonzero if a character is waiting from the console.
Write a character to the console, used by gets(), ngets(), *printf(), panic() and twiddle() and thus by many other functions for
debugging and informational output.
int devopen(struct open_file *of, const char *name, const char **file)
Open the appropriate device for the file named in name, returning in file a pointer to the remaining body of name which does not
refer to the device. The f_dev field in of will be set to point to the devsw structure for the opened device if successful.
Device identifiers must always precede the path component, but may otherwise be arbitrarily formatted. Used by open() and thus
for all device-related I/O.
int devclose(struct open_file *of)
Close the device allocated for of. The device driver itself will already have been called for the close; this call should clean
up any allocation made by devopen only.
void panic(const char *msg, ...)
Signal a fatal and unrecoverable error condition. The msg ... arguments are as for printf().
INTERNAL FILE SYSTEMS
Internal file systems are enabled by the consumer exporting the array struct fs_ops *file_system, which should be initialised with pointers
to struct fs_ops structures. The following file system handlers are supplied by libstand, the consumer may supply other file systems of
ufs_fsops The BSD UFS.
ext2fs_fsops Linux ext2fs file system.
tftp_fsops File access via TFTP.
nfs_fsops File access via NFS.
cd9660_fsops ISO 9660 (CD-ROM) file system.
gzipfs_fsops Stacked file system supporting gzipped files. When trying the gzipfs file system, libstand appends .gz to the end of the file-
name, and then tries to locate the file using the other file systems. Placement of this file system in the file_system array
determines whether gzipped files will be opened in preference to non-gzipped files. It is only possible to seek a gzipped file
forwards, and stat() and fstat() on gzipped files will report an invalid length.
bzipfs_fsops The same as gzipfs_fsops, but for bzip2(1)-compressed files.
The array of struct fs_ops pointers should be terminated with a NULL.
Devices are exported by the supporting code via the array struct devsw *devsw which is a NULL terminated array of pointers to device switch
The libstand library contains contributions from many sources, including:
o libsa from NetBSD
o libc and libkern from FreeBSD 3.0.
o zalloc from Matthew Dillon <email@example.com>
The reorganisation and port to FreeBSD 3.0, the environment functions and this manpage were written by Mike Smith <msmith@FreeBSD.org>.
The lack of detailed memory usage data is unhelpful.
BSD August 6, 2004 BSD