capture
Returns a command’s output as a string
Format
capture [ -out | -err | -both ] [ -f filename ] command
Arguments
-out
Captures only output sent to stdout.
-err
Captures only output sent to stderr.
-both
Captures output sent to both stdout and stderr. This is the default.
-f filename
Sends the captured output to filename. The file must be a writable Tcl file descriptor. Usually the Tcl file descrciptor name is obtained with open filename w.
command
The CLI command (or commands) whose output is being captured. If you specify more than one command, you must enclose them within braces ({ }).
Description
The capture command executes command, capturing in a string all output that would normally go to the console. After command completes, it returns the string. This command is analogous to the UNIX shell’s back-tick feature (`command`). The capture command obtains the printed output of any CLI command so that you can assign it to a variable or otherwise manipulate it.
Examples
set save_stat [ capture st ]
Saves the current process status to a Tcl variable.
set arg [ capture p argc]
Saves the printed value of argc into a Tcl variable.
set vbl [ capture {foreach i {1 2 3 4} {p int2_array\[$i\]}} ]
Saves the printed output of four array elements into a Tcl variable. Here is sample output:
int2_array(1) = -8 (0xfff8)
int2_array(2) = -6 (0xfffa)
int2_array(3) = -4 (0xfffc)
int2_array(4) = -2 (0xfffe)
Because the capture command records all information sent to it by the commands in the foreach loop, you do not have to use a dlist command.
exec cat << [ capture help commands ] > cli_help.txt
Writes the help text for all CLI commands to the cli_help.txt file.
set ofile [open cli_help.txt w]
capture -f $ofile help commands
close $ofile
Also writes the help text for all CLI commands to the cli_help.txt file. This set of commands is more efficient than the previous command because the captured data is not buffered.