operating system services files and directories the following functions and variables are used to manipulate files and directories on the file system to handle variances in filenaming schemesthe following variables contain information about the construction of path namesvariable description altsep an alternative character used by the os to separate pathname componentsor none if only one separator character exists this is set to '/on dos and windows systemswhere sep is backslash the string used to refer to the current working directoryfor unix and windows and ':for the macintosh the path of the null device (for example/dev/nullcharacter that separates the base filename from its type (for examplethe in 'foo txt'the string used to refer to the parent directoryfor unix and windows and '::for the macintosh the character used to separate search path components (as contained in the $path environment variable)':for unix and ';for dos and windows the character used to separate pathname components'/for unix and windows and ':for the macintosh curdir devnull extsep pardir pathsep sep the following functions are used to manipulate filesaccess(pathaccessmodechecks read/write/execute permissions for this process to access the file path accessmode is r_okw_okx_okor f_ok for readwriteexecuteor existencerespectively returns if access is granted if not chflags(pathflagschanges the file flags on path flags is the bitwise-or of the constants listed next flags starting with uf_ can be set by any userwhereas sf_ flags can only be changed by the superuser (unixflag meaning stat uf_nodump do not dump the file the file is read-only the file only supports append operations the directory is opaque the file may not be deleted or renamed the file can be archived the file is read-only the file only supports append operations the file may not be deleted or renamed the file is snapshot file stat uf_immutable stat uf_append stat uf_opaque stat uf_nounlink stat sf_archived stat sf_immutable stat sf_append stat sf_nounlink stat sf_snapshot lib fl ff