# Tools for working with parameter files

This guide describes the features and usage of the `query_paramfile` and `set_paramfile` tools, located in `tools/param_utils/`. These utilities help users inspect and modify CLM parameter files.

Note that you need to have the `ctsm_pylib` conda environment activated to use these tools. See Sect. :numref:`using-ctsm-pylib` for more information.

## `query_paramfile`
**Purpose:** Print the values of one or more parameters from a CTSM parameter file (NetCDF format).

**Features:**
- Print values for specified parameters or all.
- Optionally filter output by Plant Functional Types (PFTs) for PFT-specific parameters.

For more information, do `tools/param_utils/query_paramfile --help`.


### Example usage

Print all variables in a parameter file:
```bash
tools/param_utils/query_paramfile -i paramfile.nc
```

Print specific variables:
```bash
tools/param_utils/query_paramfile -i paramfile.nc jmaxha jmaxhd
```

Print values for specific PFTs:
```bash
tools/param_utils/query_paramfile -i paramfile.nc -p needleleaf_evergreen_temperate_tree,c4_grass medlynintercept medlynslope
```

## `set_paramfile`
**Purpose:** Change values of one or more parameters in a CTSM parameter file (NetCDF format).

**Features:**
- Modify parameter values for all or selected PFTs.
- Optionally drop PFTs not specified.
- Set parameter values to fill (missing) values using `nan`.
- Ensures safe file handling and checks for argument validity.

Note that the output file must not already exist.

For more information, do `tools/param_utils/set_paramfile --help`.

### Example usage

Change a scalar parameter:
```bash
tools/param_utils/set_paramfile -i paramfile.nc -o output.nc jmaxha=51000
```

Change a one-dimensional parameter (`mimics_fmet` has the `segment` dimension, length 4):
```bash
tools/param_utils/set_paramfile -i paramfile.nc -o output.nc mimics_fmet=0.1,0.2,0.3,0.4
```

Change a parameter for specific PFTs:
```bash
tools/param_utils/set_paramfile -i paramfile.nc -o output.nc -p needleleaf_evergreen_temperate_tree,c4_grass medlynintercept=99.9,100.1 medlynslope=2.99,1.99
```

Set a parameter to the fill value:
```bash
tools/param_utils/set_paramfile -i paramfile.nc -o output.nc -p needleleaf_evergreen_temperate_tree,c4_grass fleafcn=nan,nan
```