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LIBSTAND(3)            FreeBSD Library Functions Manual            LIBSTAND(3)

     libstand - support library for standalone executables

     #include <stand.h>

     The libstand library provides a set of supporting functions for
     standalone 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 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

     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

     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
                 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.

     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.


                 Requires <assert.h>.

     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

     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 terminated.  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 standard 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\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 ..."

     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)

     void closeall(void)

                 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.

     void pager_open()

                 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.

     void pager_close(void)

                 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

     void twiddle(void)

                 Successive calls emit the characters in the sequence |,/,-,\
                 followed by a backspace in order to provide reassurance to
                 the user.

     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
     simultaneously 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:

     int getchar(void)

                 Return a character from the console, used by gets(), ngets()
                 and pager functions.

     int ischar(void)

                 Returns nonzero if a character is waiting from the console.

     void putchar(int)

                 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

     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 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 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:
     +o   libsa from NetBSD
     +o   libc and libkern from FreeBSD 3.0.
     +o   zalloc from Matthew Dillon <>

     The reorganisation and port to FreeBSD 3.0, the environment functions and
     this manpage were written by Mike Smith <>.

     The lack of detailed memory usage data is unhelpful.

FreeBSD 11.0-PRERELEASE         August 6, 2004         FreeBSD 11.0-PRERELEASE


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