Outdated CHICKEN release

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  1. Outdated CHICKEN release
  2. Unit posix
    1. Constants
      1. File-control Commands
      2. Standard I/O file-descriptors
      3. Open flags
      4. Permission bits
    2. Directories
      1. change-directory
      2. change-directory*
      3. current-directory
      4. create-directory
      5. delete-directory
      6. directory
      7. directory?
      8. glob
      9. 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?
      13. file-type
      14. character-device?
      15. block-device?
      16. socket?
    7. Changing file attributes
      1. file-truncate
      2. set-file-position!
      3. change-file-mode
      4. change-file-owner
      5. file-creation-mode
    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
    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 codes
    14. Environment access
      1. get-environment-variables
      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
      5. Memory Mapped I/O Example
    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
      8. string->time
    17. Raw exit
      1. _exit
    18. ERRNO values
    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?
      3. terminal-size
    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).

Constants

File-control Commands

[constant] fcntl/dupfd
[constant] fcntl/getfd
[constant] fcntl/setfd
[constant] fcntl/getfl
[constant] fcntl/setfl

Operations used with file-control.

Standard I/O file-descriptors

[constant] fileno/stdin
[constant] fileno/stdout
[constant] fileno/stderr

Standard I/O file descriptor numbers, used with procedures such as open-input-file* which take file descriptors.

Open flags

[constant] open/rdonly
[constant] open/wronly
[constant] open/rdwr
[constant] open/read
[constant] open/write
[constant] open/creat
[constant] open/append
[constant] open/excl
[constant] open/noctty
[constant] open/nonblock
[constant] open/trunc
[constant] open/sync
[constant] open/fsync
[constant] open/binary
[constant] open/text

Open flags used with the file-open procedure. open/read is a convenience synonym for open/rdonly, as is open/write for open/wronly.

Permission bits

[constant] perm/irusr
[constant] perm/iwusr
[constant] perm/ixusr
[constant] perm/irgrp
[constant] perm/iwgrp
[constant] perm/ixgrp
[constant] perm/iroth
[constant] perm/iwoth
[constant] perm/ixoth
[constant] perm/irwxu
[constant] perm/irwxg
[constant] perm/irwxo
[constant] perm/isvtx
[constant] perm/isuid
[constant] perm/isgid

Permission bits used with, for example, file-open.

Directories

change-directory

[procedure] (change-directory NAME)

Changes the current working directory to NAME.

change-directory*

[procedure] (change-directory* FD)

Changes the current working directory to the one represented by the file-descriptor FD, which should be an exact integer.

current-directory

[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).

create-directory

[procedure] (create-directory NAME #!optional PARENTS?)

Creates a directory with the pathname NAME. If the PARENTS? argument is given and not false, any nonexistent parent directories are also created.

Notice that if NAME exists, create-directory won't try to create it and will return NAME (i.e., it won't raise an error when given a NAME that already exists).

delete-directory

[procedure] (delete-directory NAME [RECURSIVE])

Deletes the directory with the pathname NAME. If RECURSIVE is not given or false, then the directory has to be empty.

directory

[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.

directory?

[procedure] (directory? FILE)

Returns #t if FILE designates directory. Otherwise, it returns #f. FILE may be a pathname, a file-descriptor or a port object.

glob

[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).

set-root-directory!

[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.

Pipes

call-with-input-pipe

call-with-output-pipe

[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.

close-input-pipe

close-output-pipe

[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.

create-pipe

[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.

open-input-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.

open-output-pipe

[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.

pipe/buf

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

with-input-from-pipe

with-output-to-pipe

[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.

(with-output-to-pipe
  "gs -dNOPAUSE -sDEVICE=jpeg -dBATCH -sOutputFile=signballs.jpg -g600x600 -q -"
  (lambda ()
    (print #<<EOF
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 H/A/copy(z&v4QX&93r9AxYQOZomQalxS2w!!O&vMYa43d6r93rMYvx2dca!D&cjSnjSnjjS3o!v&6A
 X&55SAxM1CD7AjYxTTd62rmxCnTdSST0g&12wECST!&!J0g&D1!&xM0!J0g!l&544dC2Ac96ra!m&3A
 F&&vGoGSnCT0g&wDmlvGoS8wpn6wpS2wTCpS1Sd7ov7Uk7o4Qkdw!&Mvlx1S7oZES3w!J!J!Q&7185d
 Z&lx1CS9d9nE4!k&X&MY7!&1!J!x&jdnjdS3odS!N&mmx1C2wEc!G&150Nx4!n&2o!j&43r!U&0777d
 ]&2AY2A776ddT4oS3oSnMVC00VV0RRR45E42063rNz&v7UX&UOzF!F!J![&44ETCnVn!a&1CDN!Y&0M
 V1c&j2AYdjmMdjjd!o&1r!M){( )T 0 4 3 r put T(/)g{T(9)g{cvn}{cvi}J}{($)g[]J}J
 cvx}forall/moveto/p/floor/w/div/S/add 29 H[{[{]setgray fill}for Y}for showpage
 EOF
 ) ) )

Fifos

create-fifo

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

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

 (+ perm/irwxu perm/irwxg perm/irwxo)

fifo?

[procedure] (fifo? FILE)

Returns #t if FILE names a FIFO. FILE may be a filename, a port or a file-descriptor.

File descriptors and low-level I/O

duplicate-fileno

[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.

file-close

[procedure] (file-close FILENO)

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

file-open

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

Opens the file specified with the string FILENAME and open-flags FLAGS using the C function open(2). On success a file-descriptor for the opened file is returned.

FLAGS is a bitmask of open/... values ored together using bitwise-ior (or simply added together). You must provide exactly one of the access flags open/rdonly, open/wronly, or open/rdwr. Additionally, you may provide zero or more creation flags (open/creat, open/excl, open/trunc, and open/noctty) and status flags (the remaining open/... values). For example, to open a possibly new output file for appending:

(file-open "/tmp/hen.txt" (+ open/wronly open/append open/creat))

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.

file-mkstemp

[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)))

file-read

[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.

file-select

[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 ().

file-write

[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.

file-control

[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.

open-input-file*

open-output-file*

[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).

port->fileno

[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

file-access-time

file-change-time

file-modification-time

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

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.

file-access-time, file-change-time and file-modification-time also accept a port object as their argument.

(set! (file-modification-time FILE) SECONDS) sets the access- and modification time of FILE to SECONDS.

file-stat

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

Returns a 13-element vector with the following contents:

index value field notes
0 inode number st_ino
1 mode st_mode bitfield combining file permissions and file type
2 number of hard links st_nlink
3 UID of owner st_uid as with file-owner
4 GID of owner st_gid
5 size st_size as with file-size
6 access time st_atime as with file-access-time
7 change time st_ctime as with file-change-time
8 modification time st_mtime as with file-modification-time
9 parent device ID st_dev ID of device on which this file resides
10 device ID st_rdev device ID for special files (i.e. the raw major/minor number)
11 block size st_blksize
12 number of blocks allocated st_blocks

On Windows systems, the last 4 values are undefined.

By default, symbolic links are followed and the status of the referenced file is returned; however, if the optional argument LINK is given and not #f, the status of the link itself is returned.

FILE may be a filename, port or file-descriptor.

Note that for very large files, the file-size value may be an inexact integer.

file-position

[procedure] (file-position FILE)

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

file-size

[procedure] (file-size FILE)

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

regular-file?

[procedure] (regular-file? FILE)

Returns true, if FILE names a regular file (not a directory, socket, etc.) This operation follows symbolic links; use either symbolic-link? or file-type if you need to test for symlinks. FILE may refer to a filename, file descriptor or ports object.

file-owner

[procedure] (file-owner FILE)

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

file-permissions

[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, a file-descriptor or a port object.

file-read-access?

file-write-access?

file-execute-access?

[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.

file-type

[procedure] (file-type FILE [LINK [ERROR]])

Returns the file-type for FILE, which should be a filename, a file-descriptor or a port object. If LINK is given and true, symbolic-links are not followed:

 regular-file
 directory
 fifo
 socket
 symbolic-link
 character-device
 block-device

Note that not all types are supported on every platform. If ERROR is given and false, then file-type returns #f if the file does not exist; otherwise, it signals an error.

character-device?

block-device?

socket?

[procedure] (character-device? FILE)
[procedure] (block-device? FILE)
[procedure] (socket? FILE)

These procedures return #t if FILE given is of the appropriate type. FILE may be a filename, a file-descriptor or a port object. Note that these operations follow symbolic links. If the file does not exist, #f is returned.

Changing file attributes

file-truncate

[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.

set-file-position!

[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)

change-file-mode

[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.

change-file-owner

[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.

file-creation-mode

[procedure] (file-creation-mode [MODE])

Returns the initial file permissions used for newly created files (as with umask(2)). If MODE is supplied, the mode is changed to this value. You can set the mode by executing

 (set! (file-creation-mode) MODE)

or

 (file-creation-mode MODE)

where MODE is a bitwise combination of one or more of the perm/... flags.

Processes

current-process-id

[procedure] (current-process-id)

Returns the process ID of the current process.

parent-process-id

[procedure] (parent-process-id)

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

process-group-id

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

Get or set the process group ID of the process specified by PID.

process-execute

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

Replaces the running process with a new process image from the program stored at PATHNAME, 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.

This procedure never returns; it either replaces the process with a new one or it raises an exception in case something went wrong executing the program.

process-fork

[procedure] (process-fork [THUNK [KILLOTHERS?]])

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. If THUNK is given and the optional argument KILLOTHERS? is true, then kill all other existing threads in the child process, leaving only the current thread to run THUNK and terminate.

process-run

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

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

process-signal

[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.

process-wait

[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:

Note that suspending the current process implies that all threads are suspended as well.

process

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

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.

Standard error for the subprocess is linked up to the current process's standard error (see process* if you want to reify its standard error into a separate port).

Not using the shell may be preferrable for security reasons.

Once both the input- and output ports are closed, an implicit waitpid(3) is done to wait for the subprocess to finish or to reap a subprocess that has terminated. If the subprocess has not finished, waiting for it will necessarily block all executing threads.

process*

[procedure] (process* COMMANDLINE)
[procedure] (process* COMMAND ARGUMENT-LIST [ENVIRONMENT-LIST])

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.

sleep

[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.

create-session

[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? FILE)

Returns true, if FILE names a symbolic link. If no such file exists, #f is returned. This operation does not follow symbolic links itself. FILE could be a filename, file descriptor or port object.

[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 [CANONICALIZE])

Returns the filename to which the symbolic link FILENAME points. If CANONICALIZE is given and true, then symbolic links are resolved repeatedly until the result is not a link.

[procedure] (file-link OLDNAME NEWNAME)

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

Retrieving user & group information

current-user-id

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

Get or set the real user-id of the current process. The procedure corresponds to the getuid and setuid C functions.

current-effective-user-id

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

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

user-information

[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.

Note: on Android systems, the user-specific string is always "", since pw_gecos is not available in the C passwd struct on that platform.

current-group-id

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

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

current-effective-group-id

[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.

group-information

[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.

get-groups

[procedure] (get-groups)

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

Changing user & group information

set-groups!

[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.

initialize-groups

[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.

Record locking

file-lock

[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.

file-lock/blocking

[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.

file-test-lock

[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.

file-unlock

[procedure] (file-unlock LOCK)

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

Signal handling

set-alarm!

[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.

set-signal-handler!

signal-handler

[procedure] (signal-handler SIGNUM)

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

[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, and the corresponding signal set to SIG_IGN.

Notes

set-signal-mask!

[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.

signal-mask

[procedure] (signal-mask)

Returns the signal mask of the current process.

signal-masked?

[procedure] (signal-masked? SIGNUM)

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

signal-mask!

[procedure] (signal-mask! SIGNUM)

Masks (blocks) the signal for the code SIGNUM.

signal-unmask!

[procedure] (signal-unmask! SIGNUM)

Unmasks (unblocks) the signal for the code SIGNUM.

Signal codes

[constant] signal/term
[constant] signal/kill
[constant] signal/int
[constant] signal/hup
[constant] signal/fpe
[constant] signal/ill
[constant] signal/segv
[constant] signal/abrt
[constant] signal/trap
[constant] signal/quit
[constant] signal/alrm
[constant] signal/vtalrm
[constant] signal/prof
[constant] signal/io
[constant] signal/urg
[constant] signal/chld
[constant] signal/cont
[constant] signal/stop
[constant] signal/tstp
[constant] signal/pipe
[constant] signal/xcpu
[constant] signal/xfsz
[constant] signal/usr1
[constant] signal/usr2
[constant] signal/bus
[constant] signal/winch
[constant] signal/break

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

Environment access

get-environment-variables

[procedure] (get-environment-variables)

Returns a association list of the environment variables and their current values (see also SRFI-98).

setenv

[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.

unsetenv

[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

Memory mapped I/O takes the contents of a file descriptor and places them in memory.

memory-mapped-file?

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

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

map-file-to-memory

[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.

memory-mapped-file-pointer

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

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

unmap-file-from-memory

[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.

Memory Mapped I/O Example

 
;; example-mmap.scm
;;
;; basic example of memory mapped I/O
;;
;; This example does no error checking or cleanup, and serves
;; only to demonstrate how the mmap functions work together.
;;
(use posix)
(use lolevel)

       ; open a file using the posix module, so we have the file descriptor.
(let* ((fd   (file-open "example-mmap.scm" (+ open/rdonly open/nonblock)))
       ; fstat(2) the file descriptor fd to determine its size
       (size (file-size fd))
       ; mmap(2) the file for reading.
       (mmap (map-file-to-memory #f
                                 size
                                 prot/read
                                 (+ map/file map/shared)
                                 fd))
       ; return a pointer object to the beginning of the memory map.
       (buf  (memory-mapped-file-pointer mmap))
       ; allocate a string the same size as the file.
       (str  (make-string size)))
  ; copy the mapped memory into a string
  (move-memory! buf str size)
  (display str)
  ; alternately, print the string byte-by-byte without copying.
  (let loop ((p buf)
             (i 0))
    (unless (= i size)
      (display (integer->char (pointer-s8-ref p)))
      (loop (pointer+ p 1) (+ i 1)))))

Date and time routines

seconds->local-time

[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.

SECONDS defaults to the value of (current-seconds).

local-time->seconds

[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.

local-timezone-abbreviation

[procedure] (local-timezone-abbreviation)

Returns the abbreviation for the local timezone as a string.

seconds->string

[procedure] (seconds->string [SECONDS])

Converts the time represented in SECONDS into a local-time string of the form "Tue May 21 13:46:22 1991". SECONDS defaults to the value of (current-seconds).

seconds->utc-time

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

Similar to seconds->local-time, but interpretes SECONDS as UTC time. SECONDS defaults to the value of (current-seconds).

utc-time->seconds

[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.

time->string

[procedure] (time->string VECTOR [FORMAT])

Converts the broken down time represented in the 10 element vector VECTOR into a string of the form represented by the FORMAT string. The default time form produces something like "Tue May 21 13:46:22 1991".

The FORMAT string follows the rules for the C library procedure strftime. The default FORMAT string is "%a %b %e %H:%M:%S %Z %Y".

string->time

[procedure] (string->time TIME [FORMAT])

Converts a string of the form represented by the FORMAT string into the broken down time represented in a 10 element vector. The default time form understands something like "Tue May 21 13:46:22 1991".

The FORMAT string follows the rules for the C library procedure strptime. The default FORMAT string is "%a %b %e %H:%M:%S %Z %Y".

Raw exit

_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

[constant] errno/perm
[constant] errno/noent
[constant] errno/srch
[constant] errno/intr
[constant] errno/io
[constant] errno/noexec
[constant] errno/badf
[constant] errno/child
[constant] errno/nomem
[constant] errno/acces
[constant] errno/fault
[constant] errno/busy
[constant] errno/notdir
[constant] errno/isdir
[constant] errno/inval
[constant] errno/mfile
[constant] errno/nospc
[constant] errno/spipe
[constant] errno/pipe
[constant] errno/again
[constant] errno/rofs
[constant] errno/exist
[constant] errno/wouldblock

These variables contain error codes as returned by errno.

Finding files

find-files

[procedure] (find-files DIRECTORY #!key test action seed limit dotfiles follow-symlinks)

Recursively traverses the contents of DIRECTORY (which should be a string) and invokes the procedure action for all files in which the procedure test is true.

test may be a procedure of one argument or an irregex object, regex string or SRE expression that will be matched with a full pathname using irregex-match. test defaults to (constantly #t).

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 seed. action defaults to cons, seed 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).

If dotfiles is given and true, then files starting with a "." character will not be ignored (but note that "." and ".." are always ignored). if follow-symlinks is given and true, then the traversal of a symbolic link that points to a directory will recursively traverse the latter. By default, symbolic links are not followed.

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

This procedure's signature was changed in CHICKEN 4.6. In older versions, find-files has a different signature:

 (find-files DIRECTORY [TEST [ACTION [SEED [LIMIT]]]])

The old signature was supported until CHICKEN 4.7.3 for compatibility reasons, at which point it became invalid. The optional arguments are ignored and use their default values, and no warning is issued. One symptom is that your TEST does not work, returning every file.

Getting the hostname and system information

get-host-name

[procedure] (get-host-name)

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

system-information

[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

set-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

terminal-name

[procedure] (terminal-name PORT)

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

terminal-port?

[procedure] (terminal-port? PORT)

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

terminal-size

[procedure] (terminal-size PORT)

Returns two values, the number of columns and rows of the terminal that is connected to PORT or 0, 0 if the terminal size can not be obtained. On Windows, this procedure always returns 0, 0.

How Scheme procedures relate to UNIX C functions
change-directory
chdir
change-directory*
fchdir
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-group-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-creation-mode
umask
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-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.)

[procedure] (process-execute PATHNAME [ARGUMENT-LIST [ENVIRONMENT-LIST [EXACT-FLAG]]])
[procedure] (process COMMAND ARGUMENT-LIST [ENVIRONMENT-LIST [EXACT-FLAG]])
[procedure] (process* COMMAND ARGUMENT-LIST [ENVIRONMENT-LIST [EXACT-FLAG]])

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
errno/wouldblock
change-directory*
change-file-owner
current-user-id  current-group-id  current-effective-user-id  current-effective-group-id
set-user-id!  set-group-id!
create-session
process-group-id
create-symbolic-link  read-symbolic-link
file-truncate
file-lock  file-lock/blocking  file-unlock  file-test-lock
create-fifo  fifo?
set-alarm!
terminal-port?  terminal-name
process-fork  process-signal
parent-process-id
set-root-directory!
utc-time->seconds

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.

process-spawn

[procedure] (process-spawn MODE COMMAND [ARGUMENT-LIST [ENVIRONMENT-LIST [EXACT-FLAG]]])

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.

Returns:

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