LIBSTAND(3) BSD Library Functions Manual LIBSTAND(3)NAMElibstand — support library for standalone executables
The libstand library provides a set of supporting functions for stand‐
alone applications, mimicking where possible the standard BSD programming
environment. The following sections group these functions by kind.
Unless specifically described here, see the corresponding section 3 man‐
pages 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
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 dur‐
ing 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 enhance‐
ments 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
struct env_var * env_getenv(const char *name)
Looks up a variable in the environment and returns its entire
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
arguments 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 predefined 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 sup‐
ported 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 stan‐
dard 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
int fgetstr(char *buf, int size, int fd)
Read a line of at most size characters into buf. Line termi‐
nating characters are stripped, and the buffer is always NUL
terminated. Returns the number of characters in buf if suc‐
cessful, 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 fol‐
lowing standard conversions are supported: c,d,n,o,p,s,u,x.
The following modifiers are supported: +,-,#,*,0,field
The b conversion is provided to decode error registers. Its
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 num‐
ber 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\n" );
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 sup‐
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
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 read‐
Successive calls emit the characters in the sequence |,/,-,\
followed by a backspace in order to provide reassurance to
REQUIRED LOW-LEVEL SUPPORT
The following resources are consumed by libstand - stack, heap, console
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 simultane‐
ously 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 func‐
tions 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 format‐
ted. 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 sup‐
plied by libstand, the consumer may supply other file systems of their
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 filename, 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
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:
· libsa from NetBSD
· libc and libkern from FreeBSD 3.0.
· 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