There are two preferred, modern ways to make temporary files:
However this page is dedicated to ways to create temporary files by adding a bit of Tcl code, for people who target distributions older than Tcl 8.6 (not having file tempfile) and do not wish to depend on tcllib.
The temp directory is put in to different environment variables on different systems. Examples are:
A scriptlet to do this:
set tmpdir [pwd]
if {[file exists "/tmp"]} {set tmpdir "/tmp"}
catch {set tmpdir $::env(TRASH_FOLDER)} ;# very old Macintosh. Mac OS X doesn't have this.
catch {set tmpdir $::env(TMP)}
catch {set tmpdir $::env(TEMP)}If you just want one temp file:
set filename [file join $tmpdir [pid]]
If you want multiple tmpfiles, consider appending things like the application name, counter, time stamp, etc. For example:
set file [file join $tmpdir $appname.[pid].[incr ::globalCounter]]
DKF - Or create in a subdirectory/subfolder
if {![file exists [file join $tmpdir [pid]]]} {
file mkdir [file join $tmpdir [pid]]
}
set file [file join $tmpdir [pid] [incr ::globalCounter]]Michael Schlenker - Be aware of potential race conditions while opening temp files. The linux secure programming howto has some nice examples for the linux platform: http://en.tldp.org/HOWTO/Secure-Programs-HOWTO/avoid-race.html
To be sure to get a new tempfile (and not some evil symlink) try something like:
set access [list RDWR CREAT EXCL TRUNC]
set perm 0600
if {[catch {open $file $access $perm} fid ]} {
# something went wrong
error "Could not open tempfile."
}
# ok everything went wellI had some luck with the following procedure on a UNIX box. Maybe, somebody can check if it works for windows.
proc tempfile {prefix suffix} {
set chars "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
set nrand_chars 10
set maxtries 10
set access [list RDWR CREAT EXCL TRUNC]
set permission 0600
set channel ""
set checked_dir_writable 0
for {set i 0} {$i < $maxtries} {incr i} {
set newname $prefix
for {set j 0} {$j < $nrand_chars} {incr j} {
append newname [string index $chars [expr {int(rand() * 62)}]]
}
append newname $suffix
if {[file exists $newname]} {
after 1
} else {
if {[catch {open $newname $access $permission} channel]} {
if {!$checked_dir_writable} {
set dirname [file dirname $newname]
if {![file writable $dirname]} {
error "Directory $dirname is not writable"
}
set checked_dir_writable 1
}
} else {
# Success
return [list $newname $channel]
}
}
}
if {[string compare $channel ""]} {
error "Failed to open a temporary file: $channel"
} else {
error "Failed to find an unused temporary file name"
}
}Igor Volobouev
AMG: Here's a shorter version of the same:
proc tempfile {{filenameVar {}}} {
set chars abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789
if {$filenameVar ne {}} {
upvar 1 $filenameVar filename
}
for {set i 0} {$i < 10} {incr i} {
set filename /tmp/tcl_
for {set j 0} {$j < 10} {incr j} {
append filename [string index $chars [expr {int(rand() * 62)}]]
}
if {![catch {open $filename {RDWR CREAT EXCL} 0600} channel]} {
return $channel
}
}
error "failed to find an unused temporary file name"
}Stu - My version of mkstemp(3)
proc randazAZchar {} {
return [format %c [expr {int(rand() * 26) + [expr {int(rand() * 10) > 5 ? 97 : 65}]}]]
}
proc randazAZstring {length} {
set s {}
for {set i $length} {$i > 0} {incr i -1} {append s [randazAZchar]}
return $s
}
proc makeTempFile {template} {
if {[set xi [string first "X" $template]] == -1} {
set n $template
set p {}
set rl 0
} else {
set n [string range $template 0 [expr {$xi - 1}]]
set p [pid]
set rl [expr {[string length $template] - $xi - [string length $p]}]
if {$rl < 0} {
set p [string range $p 0 end-[expr {$rl * -1}]]
set rl 0
}
}
for {set i [expr {int(pow(26, ($rl <= 6 ? $rl : 6)))}]} {$i > 0} {incr i -1} {
set fn $n[randazAZstring $rl]$p
if {![catch {open $fn {CREAT EXCL RDWR} 0600} fd]} {
file delete $fn
return $fd
}
if {[lindex $::errorCode 1] ne "EEXIST" || [lindex $::errorCode 0] ne "POSIX"} {
break
}
}
return -code error -errorcode $::errorCode $fd
}wld
Have a look at GUID and UUID for generating unique filenames for temp-files.