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  1. Unit posix
    1. Constants
      1. File-control Commands
        1. fcntl/dupfd
        2. fcntl/getfd
        3. fcntl/setfd
        4. fcntl/getfl
        5. fcntl/setfl
      2. Standard I/O file-descriptors
        1. fileno/stdin
        2. fileno/stdout
        3. fileno/stderr
      3. Open flags
        1. open/rdonly
        2. open/wronly
        3. open/rdwr
        4. open/read
        5. open/write
        6. open/creat
        7. open/append
        8. open/excl
        9. open/noctty
        10. open/nonblock
        11. open/trunc
        12. open/sync
        13. open/fsync
        14. open/binary
        15. open/text
      4. Permission bits
        1. perm/irusr
        2. perm/iwusr
        3. perm/ixusr
        4. perm/irgrp
        5. perm/iwgrp
        6. perm/ixgrp
        7. perm/iroth
        8. perm/iwoth
        9. perm/ixoth
        10. perm/irwxu
        11. perm/irwxg
        12. perm/irwxo
        13. perm/isvtx
        14. perm/isuid
        15. perm/isgid
    2. Directories
      1. change-directory
      2. current-directory
      3. create-directory
      4. delete-directory
      5. directory
      6. directory?
      7. glob
      8. set-root-directory!
    3. Pipes
      1. call-with-input-pipe
      2. call-with-output-pipe
      3. close-input-pipe
      4. close-output-pipe
      5. create-pipe
      6. open-input-pipe
      7. open-output-pipe
      8. pipe/buf
      9. with-input-from-pipe
      10. with-output-to-pipe
    4. Fifos
      1. create-fifo
      2. fifo?
    5. File descriptors and low-level I/O
      1. duplicate-fileno
      2. file-close
      3. file-open
      4. file-mkstemp
      5. file-read
      6. file-select
      7. file-write
      8. file-control
      9. open-input-file*
      10. open-output-file*
      11. port->fileno
    6. Retrieving file attributes
      1. file-access-time
      2. file-change-time
      3. file-modification-time
      4. file-stat
      5. file-position
      6. file-size
      7. regular-file?
      8. file-owner
      9. file-permissions
      10. file-read-access?
      11. file-write-access?
      12. file-execute-access?
    7. Changing file attributes
      1. file-truncate
      2. set-file-position!
      3. change-file-mode
      4. change-file-owner
    8. Processes
      1. current-process-id
      2. parent-process-id
      3. process-group-id
      4. process-execute
      5. process-fork
      6. process-run
      7. process-signal
      8. process-wait
      9. process
      10. process*
      11. sleep
      12. create-session
    9. Hard and symbolic links
      1. symbolic-link?
      2. create-symbolic-link
      3. read-symbolic-link
      4. file-link
    10. Retrieving user & group information
      1. current-user-id
      2. current-effective-user-id
      3. user-information
      4. current-group-id
      5. current-effective-group-id
      6. group-information
      7. get-groups
    11. Changing user & group information
      1. set-groups!
      2. initialize-groups
      3. set-process-group-id!
    12. Record locking
      1. file-lock
      2. file-lock/blocking
      3. file-test-lock
      4. file-unlock
    13. Signal handling
      1. set-alarm!
      2. set-signal-handler!
      3. signal-handler
      4. set-signal-mask!
      5. signal-mask
      6. signal-masked?
      7. signal-mask!
      8. signal-unmask!
      9. signal/term
      10. signal/kill
      11. signal/int
      12. signal/hup
      13. signal/fpe
      14. signal/ill
      15. signal/segv
      16. signal/abrt
      17. signal/trap
      18. signal/quit
      19. signal/alrm
      20. signal/vtalrm
      21. signal/prof
      22. signal/io
      23. signal/urg
      24. signal/chld
      25. signal/cont
      26. signal/stop
      27. signal/tstp
      28. signal/pipe
      29. signal/xcpu
      30. signal/xfsz
      31. signal/usr1
      32. signal/usr2
      33. signal/winch
    14. Environment access
      1. current-environment
      2. setenv
      3. unsetenv
    15. Memory mapped I/O
      1. memory-mapped-file?
      2. map-file-to-memory
      3. memory-mapped-file-pointer
      4. unmap-file-from-memory
    16. Date and time routines
      1. seconds->local-time
      2. local-time->seconds
      3. local-timezone-abbreviation
      4. seconds->string
      5. seconds->utc-time
      6. utc-time->seconds
      7. time->string
    17. Raw exit
      1. _exit
    18. ERRNO values
      1. errno/perm
      2. errno/noent
      3. errno/srch
      4. errno/intr
      5. errno/io
      6. errno/noexec
      7. errno/badf
      8. errno/child
      9. errno/nomem
      10. errno/acces
      11. errno/fault
      12. errno/busy
      13. errno/notdir
      14. errno/isdir
      15. errno/inval
      16. errno/mfile
      17. errno/nospc
      18. errno/spipe
      19. errno/pipe
      20. errno/again
      21. errno/rofs
      22. errno/exist
      23. errno/wouldblock
    19. Finding files
      1. find-files
    20. Getting the hostname and system information
      1. get-host-name
      2. system-information
    21. Setting the file buffering mode
      1. set-buffering-mode!
    22. Terminal ports
      1. terminal-name
      2. terminal-port?
    23. How Scheme procedures relate to UNIX C functions
    24. Windows specific notes
      1. Procedure Changes
      2. Unsupported Definitions
      3. Additional Definitions
      4. process-spawn

Unit posix

This unit provides services as used on many UNIX-like systems. Note that the following definitions are not all available on non-UNIX systems like Windows. See below for Windows specific notes.

This unit uses the regex, scheduler, extras and utils units.

All errors related to failing file-operations will signal a condition of kind (exn i/o file).


File-control Commands


Standard I/O file-descriptors


Open flags


Permission bits




[procedure] (change-directory NAME)

Changes the current working directory to NAME.


[procedure] (current-directory [DIR])

Returns the name of the current working directory. If the optional argument DIR is given, then (current-directory DIR) is equivalent to (change-directory DIR).


[procedure] (create-directory NAME)

Creates a directory with the pathname NAME.


[procedure] (delete-directory NAME)

Deletes the directory with the pathname NAME. The directory has to be empty.


[procedure] (directory [PATHNAME [SHOW-DOTFILES?]])

Returns a list with all files that are contained in the directory with the name PATHNAME (which defaults to the value of (current-directory)). Files beginning with . are included only if SHOW-DOTFILES? is given and not #f.


[procedure] (directory? NAME)

Returns #t if there exists a file with the name NAME and if that file is a directory, or #f otherwise.


[procedure] (glob PATTERN1 ...)

Returns a list of the pathnames of all existing files matching PATTERN1 ..., which should be strings containing the usual file-patterns (with * matching zero or more characters and ? matching zero or one character).


[procedure] (set-root-directory! STRING)

Sets the root directory for the current process to the path given in STRING (using the chroot function). If the current process has no root permissions, the operation will fail.




[procedure] (call-with-input-pipe CMDLINE PROC [MODE])
[procedure] (call-with-output-pipe CMDLINE PROC [MODE])

Call PROC with a single argument: a input- or output port for a pipe connected to the subprocess named in CMDLINE. If PROC returns normally, the pipe is closed and any result values are returned.



[procedure] (close-input-pipe PORT)
[procedure] (close-output-pipe PORT)

Closes the pipe given in PORT and waits until the connected subprocess finishes. The exit-status code of the invoked process is returned.


[procedure] (create-pipe)

The fundamental pipe-creation operator. Calls the C function pipe() and returns 2 values: the file-descriptors of the input- and output-ends of the pipe.


[procedure] (open-input-pipe CMDLINE [MODE])

Spawns a subprocess with the command-line string CMDLINE and returns a port, from which the output of the process can be read. If MODE is specified, it should be the keyword #:text (the default) or #:binary.


[procedure] (open-output-pipe CMDLINE [MODE])

Spawns a subprocess with the command-line string CMDLINE and returns a port. Anything written to that port is treated as the input for the process. If MODE is specified, it should be the keyword #:text (the default) or #:binary.


This variable contains the maximal number of bytes that can be written atomically into a pipe or FIFO.



[procedure] (with-input-from-pipe CMDLINE THUNK [MODE])
[procedure] (with-output-to-pipe CMDLINE THUNK [MODE])

Temporarily set the value of current-input-port/current-output-port to a port for a pipe connected to the subprocess named in CMDLINE and call the procedure THUNK with no arguments. After THUNK returns normally the pipe is closed and the standard input-/output port is restored to its previous value and any result values are returned.

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[procedure] (create-fifo FILENAME [MODE])

Creates a FIFO with the name FILENAME and the permission bits MODE, which defaults to

 [procedure] (+ perm/irwxu perm/irwxg perm/irwxo)


[procedure] (fifo? FILENAME)

Returns #t if the file with the name FILENAME names a FIFO.

File descriptors and low-level I/O


[procedure] (duplicate-fileno OLD [NEW])

If NEW is given, then the file-descriptor NEW is opened to access the file with the file-descriptor OLD. Otherwise a fresh file-descriptor accessing the same file as OLD is returned.


[procedure] (file-close FILENO)

Closes the input/output file with the file-descriptor FILENO.


[procedure] (file-open FILENAME FLAGS [MODE])

Opens the file specified with the string FILENAME and open-flags FLAGS using the C function open(). On success a file-descriptor for the opened file is returned. FLAGS should be a bitmask containing one or more of the open/... values ored together using bitwise-ior (or simply added together). The optional MODE should be a bitmask composed of one or more permission values like perm/irusr and is only relevant when a new file is created. The default mode is perm/irwxu | perm/irgrp | perm/iroth.


[procedure] (file-mkstemp TEMPLATE-FILENAME)

Create a file based on the given TEMPLATE-FILENAME, in which the six last characters must be XXXXXX. These will be replaced with a string that makes the filename unique. The file descriptor of the created file and the generated filename is returned. See the mkstemp(3) manual page for details on how this function works. The template string given is not modified.

Example usage:

 (let-values (((fd temp-path) (file-mkstemp "/tmp/mytemporary.XXXXXX")))
  (let ((temp-port (open-output-file* fd)))
    (format temp-port "This file is ~A.~%" temp-path)
    (close-output-port temp-port)))


[procedure] (file-read FILENO SIZE [BUFFER])

Reads SIZE bytes from the file with the file-descriptor FILENO. If a string or bytevector is passed in the optional argument BUFFER, then this string will be destructively modified to contain the read data. This procedure returns a list with two values: the buffer containing the data and the number of bytes read.


[procedure] (file-select READFDLIST WRITEFDLIST [TIMEOUT])

Waits until any of the file-descriptors given in the lists READFDLIST and WRITEFDLIST is ready for input or output, respectively. If the optional argument TIMEOUT is given and not false, then it should specify the number of seconds after which the wait is to be aborted (the value may be a floating point number). This procedure returns two values: the lists of file-descriptors ready for input and output, respectively. READFDLIST and WRITEFDLIST may also by file-descriptors instead of lists. In this case the returned values are booleans indicating whether input/output is ready by #t or #f otherwise. You can also pass #f as READFDLIST or WRITEFDLIST argument, which is equivalent to ().


[procedure] (file-write FILENO BUFFER [SIZE])

Writes the contents of the string or bytevector BUFFER into the file with the file-descriptor FILENO. If the optional argument SIZE is given, then only the specified number of bytes are written.


[procedure] (file-control FILENO COMMAND [ARGUMENT])

Performs the fcntl operation COMMAND with the given FILENO and optional ARGUMENT. The return value is meaningful depending on the COMMAND.



[procedure] (open-input-file* FILENO [OPENMODE])
[procedure] (open-output-file* FILENO [OPENMODE])

Opens file for the file-descriptor FILENO for input or output and returns a port. FILENO should be a positive exact integer. OPENMODE specifies an additional mode for opening the file (currently only the keyword #:append is supported, which opens an output-file for appending).


[procedure] (port->fileno PORT)

If PORT is a file- or tcp-port, then a file-descriptor is returned for this port. Otherwise an error is signaled.

Retrieving file attributes




[procedure] (file-access-time FILE)
[procedure] (file-change-time FILE)
[procedure] (file-modification-time FILE)

Returns time (in seconds) of the last access, modification or change of FILE. FILE may be a filename or a file-descriptor. If the file does not exist, an error is signaled.


[procedure] (file-stat FILE [LINK])

Returns a 13-element vector with the following contents: inode-number, mode (as with file-permissions), number of hard links, uid of owner (as with file-owner), gid of owner, size (as with file-size) and access-, change- and modification-time (as with file-access-time, file-change-time and file-modification-time, device id, device type (for special file inode, blocksize and blocks allocated. On Windows systems the last 4 values are undefined. If the optional argument LINK is given and not #f, then the file-statistics vector will be resolved for symbolic links (otherwise symbolic links are not resolved). Note that for very large files, the file-size value may be an inexact integer.


[procedure] (file-position FILE)

Returns the current file position of FILE, which should be a port or a file-descriptor.


[procedure] (file-size FILENAME)

Returns the size of the file designated by FILE. FILE may be a filename or a file-descriptor. If the file does not exist, an error is signaled. Note that for very large files, file-size may return an inexact integer.


[procedure] (regular-file? FILENAME)

Returns true, if FILENAME names a regular file (not a directory or symbolic link).


[procedure] (file-owner FILE)

Returns the user-id of FILE. FILE may be a filename or a file-descriptor.


[procedure] (file-permissions FILE)

Returns the permission bits for FILE. You can test this value by performing bitwise operations on the result and the perm/... values. FILE may be a filename or a file-descriptor.




[procedure] (file-read-access? FILENAME)
[procedure] (file-write-access? FILENAME)
[procedure] (file-execute-access? FILENAME)

These procedures return #t if the current user has read, write or execute permissions on the file named FILENAME.

Changing file attributes


[procedure] (file-truncate FILE OFFSET)

Truncates the file FILE to the length OFFSET, which should be an integer. If the file-size is smaller or equal to OFFSET then nothing is done. FILE should be a filename or a file-descriptor.


[procedure] (set-file-position! FILE POSITION [WHENCE])
[procedure] (set! (file-position FILE) POSITION)

Sets the current read/write position of FILE to POSITION, which should be an exact integer. FILE should be a port or a file-descriptor. WHENCE specifies how the position is to interpreted and should be one of the values seek/set, seek/cur and seek/end. It defaults to seek/set.

Exceptions: (exn bounds), (exn i/o file)


[procedure] (change-file-mode FILENAME MODE)

Changes the current file mode of the file named FILENAME to MODE using the chmod() system call. The perm/... variables contain the various permission bits and can be combinded with the bitwise-ior procedure.


[procedure] (change-file-owner FILENAME UID GID)

Changes the owner information of the file named FILENAME to the user- and group-ids UID and GID (which should be exact integers) using the chown() system call.



[procedure] (current-process-id)

Returns the process ID of the current process.


[procedure] (parent-process-id)

Returns the process ID of the parent of the current process.


[procedure] (process-group-id PID)

Returns the process group ID of the process specified by PID.


[procedure] (process-execute PATHNAME [ARGUMENT-LIST [ENVIRONMENT-LIST]])

Creates a new child process and replaces the running process with it using the C library function execvp(3). If the optional argument ARGUMENT-LIST is given, then it should contain a list of strings which are passed as arguments to the subprocess. If the optional argument ENVIRONMENT-LIST is supplied, then the library function execve(2) is used, and the environment passed in ENVIRONMENT-LIST (which should be of the form ("<NAME>=<VALUE>" ...) is given to the invoked process. Note that execvp(3) respects the current setting of the PATH environment variable while execve(3) does not.


[procedure] (process-fork [THUNK])

Creates a new child process with the UNIX system call fork(). Returns either the PID of the child process or 0. If THUNK is given, then the child process calls it as a procedure with no arguments and terminates.


[procedure] (process-run COMMANDLINE])
[procedure] (process-run COMMAND ARGUMENT-LIST)

Creates a new child process. The PID of the new process is returned.


[procedure] (process-signal PID [SIGNAL])

Sends SIGNAL to the process with the id PID using the UNIX system call kill(). SIGNAL defaults to the value of the variable signal/term.


[procedure] (process-wait [PID [NOHANG]])

Suspends the current process until the child process with the id PID has terminated using the UNIX system call waitpid(). If PID is not given, then this procedure waits for any child process. If NOHANG is given and not #f then the current process is not suspended. This procedure returns three values:


[procedure] (process COMMANDLINE)

Creates a subprocess and returns three values: an input port from which data written by the sub-process can be read, an output port from which any data written to will be received as input in the sub-process and the process-id of the started sub-process. Blocking reads and writes to or from the ports returned by process only block the current thread, not other threads executing concurrently.

Not using the shell may be preferrable for security reasons.


[procedure] (process* COMMANDLINE)

Like process but returns 4 values: an input port from which data written by the sub-process can be read, an output port from which any data written to will be received as input in the sub-process, the process-id of the started sub-process, and an input port from which data written by the sub-process to stderr can be read.


[procedure] (sleep SECONDS)

Puts the process to sleep for SECONDS. Returns either 0 if the time has completely elapsed, or the number of remaining seconds, if a signal occurred.


[procedure] (create-session)

Creates a new session if the calling process is not a process group leader and returns the session ID.

[procedure] (symbolic-link? FILENAME)

Returns true, if FILENAME names a symbolic link.

[procedure] (create-symbolic-link OLDNAME NEWNAME)

Creates a symbolic link with the filename NEWNAME that points to the file named OLDNAME.

[procedure] (read-symbolic-link FILENAME)

Returns the filename to which the symbolic link FILENAME points.

[procedure] (file-link OLDNAME NEWNAME)

Creates a hard link from OLDNAME to NEWNAME (both strings).

Retrieving user & group information


[procedure] (current-user-id)
[setter] (set! (current-user-id) UID)

Get or set the real user-id of the current process.


[procedure] (current-effective-user-id)
[setter] (set! (current-effective-user-id) UID)

Get or set the effective user-id of the current process.


[procedure] (user-information USER [AS-VECTOR])

If USER specifes a valid username (as a string) or user ID, then the user database is consulted and a list of 7 values are returned: the user-name, the encrypted password, the user ID, the group ID, a user-specific string, the home directory and the default shell. When AS-VECTOR is #t a vector of 7 elements is returned instead of a list. If no user with this name or id then #f is returned.


[procedure] (current-group-id)
[setter] (set! (current-group-id) GID)

Get or set the real group-id of the current process.


[procedure] (current-effective-group-id)
[setter] (set! (current-effective-group-id) GID)

Get or set the effective group-id of the current process. ID can be found, then #f is returned.


[procedure] (group-information GROUP)

If GROUP specifies a valid group-name or group-id, then this procedure returns a list of four values: the group-name, the encrypted group password, the group ID and a list of the names of all group members. If no group with the given name or ID exists, then #f is returned.


[procedure] (get-groups)

Returns a list with the supplementary group IDs of the current user.

Changing user & group information


[procedure] (set-groups! GIDLIST)

Sets the supplementrary group IDs of the current user to the IDs given in the list GIDLIST.

Only the superuser may invoke this procedure.


[procedure] (initialize-groups USERNAME BASEGID)

Sets the supplementrary group IDs of the current user to the IDs from the user with name USERNAME (a string), including BASEGID.

Only the superuser may invoke this procedure.


[procedure] (set-process-group-id! PID PGID)
[setter] (set! (process-group-id PID) PGID)

Sets the process group ID of the process specifed by PID to PGID.

Record locking


[procedure] (file-lock PORT [START [LEN]])

Locks the file associated with PORT for reading or writing (according to whether PORT is an input- or output-port). START specifies the starting position in the file to be locked and defaults to 0. LEN specifies the length of the portion to be locked and defaults to #t, which means the complete file. file-lock returns a lock-object.


[procedure] (file-lock/blocking PORT [START [LEN]])

Similar to file-lock, but if a lock is held on the file, the current process blocks (including all threads) until the lock is released.


[procedure] (file-test-lock PORT [START [LEN]])

Tests whether the file associated with PORT is locked for reading or writing (according to whether PORT is an input- or output-port) and returns either #f or the process-id of the locking process.


[procedure] (file-unlock LOCK)

Unlocks the previously locked portion of a file given in LOCK.

Signal handling


[procedure] (set-alarm! SECONDS)

Sets an internal timer to raise the signal/alrm after SECONDS are elapsed. You can use the set-signal-handler! procedure to write a handler for this signal.


[procedure] (set-signal-handler! SIGNUM PROC)

Establishes the procedure of one argument PROC as the handler for the signal with the code SIGNUM. PROC is called with the signal number as its sole argument. If the argument PROC is #f then any signal handler will be removed.

Note that is is unspecified in which thread of execution the signal handler will be invoked.


[procedure] (signal-handler SIGNUM)

Returns the signal handler for the code SIGNUM or #f.


[procedure] (set-signal-mask! SIGLIST)

Sets the signal mask of the current process to block all signals given in the list SIGLIST. Signals masked in that way will not be delivered to the current process.


[procedure] (signal-mask)

Returns the signal mask of the current process.


[procedure] (signal-masked? SIGNUM)

Returns whether the signal for the code SIGNUM is currently masked.


[procedure] (signal-mask! SIGNUM)

Masks (blocks) the signal for the code SIGNUM.


[procedure] (signal-unmask! SIGNUM)

Unmasks (unblocks) the signal for the code SIGNUM.


























These variables contain signal codes for use with process-signal, set-signal-handler!, signal-handler, signal-masked?, signal-mask!, or signal-unmask!.

Environment access


[procedure] (current-environment)

Returns a association list of the environment variables and their current values.


[procedure] (setenv VARIABLE VALUE)

Sets the environment variable named VARIABLE to VALUE. Both arguments should be strings. If the variable is not defined in the environment, a new definition is created.


[procedure] (unsetenv VARIABLE)

Removes the definition of the environment variable VARIABLE from the environment of the current process. If the variable is not defined, nothing happens.

Memory mapped I/O


[pocedure] (memory-mapped-file? X)

Returns #t, if X is an object representing a memory mapped file, or #f otherwise.


[procedure] (map-file-to-memory ADDRESS LEN PROTECTION FLAG FILENO [OFFSET])

Maps a section of a file to memory using the C function mmap(). ADDRESS should be a foreign pointer object or #f; LEN specifies the size of the section to be mapped; PROTECTION should be one or more of the flags prot/read, prot/write, prot/exec or prot/none bitwise-iored together; FLAG should be one or more of the flags map/fixed, map/shared, map/private, map/anonymous or map/file; FILENO should be the file-descriptor of the mapped file. The optional argument OFFSET gives the offset of the section of the file to be mapped and defaults to 0. This procedure returns an object representing the mapped file section. The procedure move-memory! can be used to access the mapped memory.


[procedure] (memory-mapped-file-pointer MMAP)

Returns a machine pointer to the start of the memory region to which the file is mapped.


[procedure] (unmap-file-from-memory MMAP [LEN])

Unmaps the section of a file mapped to memory using the C function munmap(). MMAP should be a mapped file as returned by the procedure map-file-to-memory. The optional argument LEN specifies the length of the section to be unmapped and defaults to the complete length given when the file was mapped.

Date and time routines


[procedure] (seconds->local-time SECONDS)

Breaks down the time value represented in SECONDS into a 10 element vector of the form #(seconds minutes hours mday month year wday yday dstflag timezone), in the following format:

seconds (0)
the number of seconds after the minute (0 - 59)
minutes (1)
the number of minutes after the hour (0 - 59)
hours (2)
the number of hours past midnight (0 - 23)
mday (3)
the day of the month (1 - 31)
month (4)
the number of months since january (0 - 11)
year (5)
the number of years since 1900
wday (6)
the number of days since Sunday (0 - 6)
yday (7)
the number of days since January 1 (0 - 365)
dstflag (8)
a flag that is true if Daylight Saving Time is in effect at the time described.
timezone (9)
the difference between UTC and the latest local standard time, in seconds west of UTC.


[procedure] (local-time->seconds VECTOR)

Converts the ten-element vector VECTOR representing the time value relative to the current timezone into the number of seconds since the first of January, 1970 UTC.


[procedure] (local-timezone-abbreviation)

Returns the abbreviation for the local timezone as a string.


[procedure] (seconds->string SECONDS)

Converts the local time represented in SECONDS into a string of the form "Tue May 21 13:46:22 1991".


[procedure] (seconds->utc-time SECONDS)

Similar to seconds->local-time, but interpretes SECONDS as UTC time.


[procedure] (utc-time->seconds VECTOR)

Converts the ten-element vector VECTOR representing the UTC time value into the number of seconds since the first of January, 1970 UTC.


[procedure] (time->string VECTOR)

Converts the broken down time represented in the 10 element vector VECTOR into a string of the form "Tue May 21 13:46:22 1991".

Raw exit


[procedure] (_exit [CODE])

Exits the current process without flushing any buffered output (using the C function _exit). Note that the exit-handler is not called when this procedure is invoked. The optional return-code CODE defaults to 0.

ERRNO values
























These variables contain error codes as returned by errno.

Finding files



Recursively traverses the contents of DIRECTORY (which should be a string) and invokes the procedure ACTION for all files in which the procedure PREDICATE is true. PREDICATE may me a procedure of one argument or a regular-expression string. ACTION should be a procedure of two arguments: the currently encountered file and the result of the previous invocation of ACTION, or, if this is the first invocation, the value of IDENTITY. ACTION defaults to cons, IDENTITY defaults to (). LIMIT should be a procedure of one argument that is called for each nested directory and which should return true, if that directory is to be traversed recursively. LIMIT may also be an exact integer that gives the maximum recursion depth. For example, a depth of 0 means that only files in the top-level, specified directory are to be traversed. In this case, all nested directories are ignored. LIMIT may also be #f (the default), which is equivalent to (constantly #t).

Note that ACTION is called with the full pathname of each file, including the directory prefix.

Getting the hostname and system information


[procedure] (get-host-name)

Returns the hostname of the machine that this process is running on.


[procedure] (system-information)

Invokes the UNIX system call uname() and returns a list of 5 values: system-name, node-name, OS release, OS version and machine.

Setting the file buffering mode


[procedure] (set-buffering-mode! PORT MODE [BUFSIZE])

Sets the buffering-mode for the file associated with PORT to MODE, which should be one of the keywords #:full, #:line or #:none. If BUFSIZE is specified it determines the size of the buffer to be used (if any).

Terminal ports


[procedure] (terminal-name PORT)

Returns the name of the terminal that is connected to PORT.


[procedure] (terminal-port? PORT)

Returns #t if PORT is connected to a terminal and #f otherwise.

How Scheme procedures relate to UNIX C functions

change-directory chdir
change-file-mode chmod
change-file-owner chown
create-directory mkdir
create-fifo mkfifo
create-pipe pipe
create-session setsid
create-symbolic-link link
current-directory curdir
current-effective-groupd-id getegid
current-effective-user-id geteuid
current-group-id getgid
current-parent-id getppid
current-process-id getpid
current-user-id getuid
delete-directory rmdir
duplicate-fileno dup/dup2
_exit _exit
file-close close
file-access-time stat
file-change-time stat
file-modification-time stat
file-execute-access? access
file-open open
file-lock fcntl
file-position ftell/lseek
file-read read
file-read-access? access
file-select select
file-control fcntl
file-stat stat
file-test-lock fcntl
file-truncate truncate/ftruncate
file-unlock fcntl
file-write write
file-write-access? access
get-groups getgroups
get-host-name gethostname
initialize-groups initgroups
local-time->seconds mktime
local-timezone-abbreviation localtime
map-file-to-memory mmap
open-input-file* fdopen
open-output-file* fdopen
open-input-pipe popen
open-output-pipe popen
port->fileno fileno
process-execute execvp
process-fork fork
process-group-id getpgid
process-signal kill
process-wait waitpid
close-input-pipe pclose
close-output-pipe pclose
read-symbolic-link readlink
seconds->local-time localtime
seconds->string ctime
seconds->utc-time gmtime
set-alarm! alarm
set-buffering-mode! setvbuf
set-file-position! fseek/seek
set-groups! setgroups
set-signal-mask! sigprocmask
set-group-id! setgid
set-process-group-id! setpgid
set-user-id! setuid
set-root-directory! chroot
setenv setenv/putenv
sleep sleep
system-information uname
terminal-name ttyname
terminal-port? isatty
time->string asctime
unsetenv putenv
unmap-file-from-memory munmap
user-information getpwnam/getpwuid
utc-time->seconds timegm

Windows specific notes

Use of UTF8 encoded strings is for pathnames is not supported. Windows uses a 16-bit UNICODE encoding with special system calls for wide-character support. Only single-byte string encoding can be used.

Procedure Changes

Exceptions to the above procedure definitions.

[procedure] (create-pipe [MODE])

The optional parameter MODE, default open/binary | open/noinherit. This can be open/binary or open/text, optionally or'ed with open/noinherit.

[procedure] (process-wait [PID [NOHANG]])

process-wait always returns #t for a terminated process and only the exit status is available. (Windows does not provide signals as an interprocess communication method.)


The optional parameter EXACT-FLAG, default #f. When #f any argument string with embedded whitespace will be wrapped in quotes. When #t no such wrapping occurs.

Unsupported Definitions

The following definitions are not supported for native Windows builds (compiled with the Microsoft tools or with MinGW):

open/noctty  open/nonblock  open/fsync  open/sync
perm/isvtx  perm/isuid  perm/isgid
file-select file-control
signal/... (except signal/term, signal/int, signal/fpe, signal/ill, signal/segv, signal/abrt, signal/break)
set-signal-mask!  signal-mask  signal-masked?  signal-mask!  signal-unmask!
user-information  group-information  get-groups  set-groups!  initialize-groups
current-user-id  current-group-id  current-effective-user-id  current-effective-groupd-id
set-user-id!  set-group-id!
process-group-id  set-process-group-id!
create-symbolic-link  read-symbolic-link
file-lock  file-lock/blocking  file-unlock  file-test-lock
create-fifo  fifo?
map-file-to-memory  unmap-file-from-memory  memory-mapped-file-pointer  memory-mapped-file?
terminal-port?  terminal-name
process-fork  process-signal

Additional Definitions

Only available for Windows

This variable is a mode value for create-pipe. Useful when spawning a child process.

These variables contains special flags that specify the exact semantics of process-spawn: spawn/overlay replaces the current process with the new one. spawn/wait suspends execution of the current process until the spawned process returns. spawn/nowait does the opposite (spawn/nowaito is identical, according to the Microsoft documentation) and runs the process asynchronously. spawn/detach runs the new process in the background, without being attached to a console.



Creates and runs a new process with the given COMMAND filename and the optional ARGUMENT-LIST and ENVIRONMENT-LIST. MODE specifies how exactly the process should be executed and must be one or more of the spawn/... flags defined above.

The EXACT-FLAG, default #f, controls quote-wrapping of argument strings. When #t quote-wrapping is not performed.


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