spec
Software for Diffraction
2.4.1.1. - System Functions
chdir()-
Changes spec's current working directory to
to the user's home directory as obtained from the user's
environment variable
HOME.
Returns
true or false according to whether the
command was successful or not.
The value of the built-in string variable
CWD is updated to the current working directory.
chdir(directory)-
As above, but changes to the directory
directory,
which must be a string constant or expression.
unix()-
Spawns an interactive
subshell using the
program obtained from the user's
environment variable
SHELL
(or
shell).
Uses
/bin/sh
if the
environment variable is not set.
Returns the integer exit status of the shell.
unix(command)-
As above, but uses
/bin/sh
to execute the one-line
command
command,
which must be a string constant or expression.
Returns the integer exit status of the command.
unix(command, str [, len ])-
As above, but the argument
str
is the name of a variable in which to place the string output
from the command in the first argument.
The maximum length of the string is 4096 bytes (including a null byte).
The optional third argument can be used to specify a larger
size.
time()-
Returns the current epoch in seconds.
The UNIX epoch
is the number of seconds from
January 1, 1970,
00:00:00 GMT.
The value returned includes a fractional part with microsecond
resolution as provided by the host
gettimeofday()
system call.
date()-
Returns a string containing the current
date as
Tue Feb 7 21:02:23 EST 2017
date(fmt)-
As above, but the output string is formatted according
to the specifications in the string
fmt.
The format is passed to
the standard C library
strftime()
function (see the
strftime
man
page) with one addition: spec fills in the format options
%.1 through
%.9 with the fractional seconds, where the single digit
specifies the number of decimal digits.
For example,
print date("%m-%d-%Y %T.%.6")
would display
02-07-2017 21:04:57.927905
date(seconds [, fmt)-
As above, but the returned string
represents the epoch given by
seconds.
See
time() above.
getenv(string)-
Returns the value of the environment variable represented by
the string
string.
If the environment variable is unset, the null string is returned.
Environment variables are exported to spec by the invoking shell program.
file_info(filename [, cmd ])-
Returns information on the file or device named
filename.
With a single
filename
argument,
file_info() returns
true if the file or device exists.
If the argument
filename
is the string
"?", the possible values for
cmd
are listed.
If
filename
is the string
".", spec uses the information from the last
stat()
system call made using the previous argument for
filename,
avoiding the overhead associated with an additional
system call.
Possible values for
"dev" - The device number on which
filename
resides.
"ino" - The inode number of
filename.
"mode" - A number coding the access modes and file attributes.
"nlink" - The number of hard links for
filename.
"uid" - The user id of the owner.
"gid" - The group id of the owner.
"rdev" - The device ID if
filename
is a block or character device.
"size" - The size in bytes of
filename.
"atime" - The time when
filename's
data was last accessed.
"mtime" - The time when
filenames's
data was last modified.
"ctime" - The time when
filenames's
attributes were last modified.
"isreg" or "-f"-
Returns
true if
filename
is a regular file.
"isdir" or "-d"-
Returns
true if
filename
is a directory.
"ischr" or "-c"-
Returns
true if
filename
is a character device.
"isblk" or "-b"-
Returns
true if
filename
is a block device.
"islnk" or "-h or @-L"-
Returns
true if
filename
is a symbolic link.
"isfifo" or "-p"-
Returns
true if
filename
is a
named pipe
(sometimes called a
fifo).
"issock" or "-S"-
Returns
true if
filename
is a socket.
"-e" - Returns
true if
filename
exists.
"-s" - Returns
true if the size of
filename
is greater than zero.
"-r" - Returns
true if
filename
is readable.
"-w" - Returns
true if
filename
is writable.
"-x" - Returns
true if
filename
is executable.
"-o" - Returns
true if
filename
is owned by you.
"-G" - Returns
true if
filename
is owned by your group.
"-u" - Returns
true if
filename
is setuid mode.
"-g" - Returns
true if
filename
is setguid mode.
"-k" - Returns
true if
filename
has its sticky bit set.
"lines" - Returns the
number of newline characters in the file.
If the file does not end with a newline, the count is increased by one.
file_info(pid, "alive")-
Return
true if the process associated with the process ID
pid
exists.
