# Recorder Commands
<noinclude>This command is used to generate a recorder object
which is to monitor what is happening during the analysis and generate
output for the user.
```tcl
recorder recorderType? arg1? ...
```
-
To record the nodal response and response sensitivity, the most commonly
used format is:
```tcl
recorder Node -file disp29.out -time -node 29 -dof 1
<-precision 16 > disp
```
recorder Node -file ddm29G1.out -time -node 29 -dof 1
"sensitivity 1" |
recorder Node -file ddm29G1.out -time -node 29 -dof 1
"velSensitivity 1" |
```tcl
recorder Node -file ddm29G1.out -time -node 29 -dof 1
"accSensitivity 1"
```
-
The above ‘recorder’ commands (extended for recording response
sensitivities) save into files (with the file name defined after : the
command ‘-file’) the responses and response sensitivities of the node 29
along the first degree of freedom (dof) direction. : Response quantities
can be ‘disp’ (displacements), ‘vel’ (velocities) and ‘acc’
(accelerations). Response sensitivities are
-
denoted by a string in double quotes and containing the response
quantity identifier (i.e., “sensitivity” for displacements,
-
“velSensitivity” for velocities and “accSensitivity” for accelerations)
and the sensitivity parameter specified by the parameter : tag ( in this
example the tag is 1).
-
The command ‘-precision’ is optional, and allows users to change the
number of digits used to record into file the response
-
and/or response sensitivities. This command is particularly useful when
the finite difference method is used to verify/validate : DDM-based FE
response sensitivities, since high accuracy in the results may be
needed.
-
The user may also get responses and response sensitivities directly
using the following Tcl commands:
```tcl
sensNodeAccel 29 1 2
```
-
These commands return the responses of the node 29 along the first dof,
and their response sensitivities with respect to the
-
parameter with tag 2