trick/docs/documentation/building_a_simulation/Environment-Variables.md

Trick uses a list of variables for building sims e.g. TRICK_CFLAGS and TRICK_CXXFLAGS.  Each variable has a default value that may be overridden by setting the value in the environment. Trick resolves these variables by a call to a function called "trick-gte". Type in "${TRICK_HOME}/bin/trick-gte" on the command line to see what the "Trick environment" is.

### Adding ${TRICK_HOME}/bin to PATH

${TRICK_HOME}/bin can be added to the PATH environment variable for convenience. It is not necessary for compiling or running sims but allows you to call Trick's functions without using the full path of Trick's executables.

```
# bash
PATH="${PATH}:/path/to/trick"

# [t]csh
setenv PATH "${PATH}:/path/to/trick"
```

### TRICK_CFLAGS and TRICK_CXXFLAGS

The contents of TRICK_CFLAGS is included on the command line with each C file compilation. Similarly, TRICK_CXXFLAGS is included for each C++ file. Each contain header file search directories, macro define variables, and compiler flags.

For building a simulation, a user must be proficient at tweaking TRICK_CFLAGS and TRICK_CXXFLAGS. There are a several ways to do this.

TRICK_CXXFLAGS works exactly like TRICK_CFLAGS.

Example 1: Add "-I/user/mooo/trick_models" to the environment variable. TRICK_CFLAGS is currently...

```
UNIX Prompt> echo $TRICK_CFLAGS
-Wall
```

Now we need to edit the shell startup file where TRICK_CFLAGS is defined.

Add the following line for bash.

```
TRICK_CFLAGS="$TRICK_CFLAGS -I/user/mooo/trick_models"
```

Add the following line for [t]csh.

```
setenv TRICK_CFLAGS "$TRICK_CFLAGS -I/user/mooo/trick_models"
```

Now source your shell startup file and voila!...

For bash:
```
UNIX Prompt> . ~/.bash_profile
UNIX Prompt> echo $TRICK_CFLAGS
-Wall -I/user/mooo/trick_models
```

For [t]csh:
```
UNIX Prompt> source ~/.cshrc
UNIX Prompt> echo $TRICK_CFLAGS
-Wall -I/user/mooo/trick_models
```

Example 2: Add "-I/user/mooo/trick_models" through the simulation S_overrides.mk file

We need to edit the S_overrides.mk file in the simulation to be built.

Add the following line.

```
TRICK_CFLAGS="$TRICK_CFLAGS -I/user/mooo/trick_models"
```

This will not show up in the current shell environment, but will be set for each command that the makefile executes.

### TRICK_CONVERT_SWIG_FLAGS

TRICK_CONVERT_SWIG_FLAGS contains flags sent to the convert_swig utility. Currently the flags only support "-s" which allows convert_swig to process STLs.

### TRICK_SWIG_FLAGS and TRICK_SWIG_CFLAGS

TRICK_SWIG_FLAGS are the options that are passed to SWIG (see the SWIG documentation). TRICK_SWIG_CFLAGS are the the options passed to the c/c++ compiler when compiling SWIG objects. 

### TRICK_EXCLUDE

A colon separated list of directories to skip when processing files.

It is possible to instruct all CP functions to skip entire directories using the environment variable TRICK_EXCLUDE. Set this variable to a colon separated list of directories which you wish CP to bypass. All header files found in TRICK_EXCLUDE will not be processed. All source code files found in TRICK_EXCLUDE will not be compiled or linked into the simulation.

This feature is useful to bring in packages as a library.

### TRICK_FORCE_32BIT

To force Trick to compile in 32-bit on 64-bit systems, set the TRICK_FORCE_32BIT environment variable to 1. Setting this variable appends "-m32" automatically to TRICK_CFLAGS and TRICK_CXXFLAGS.
4.2.6 TRICK_HOST_CPU

Trick determines a system specific suffix to append to object code directory names. By default this is determined automatically by Trick. The user may override this by setting the TRICK_HOST_CPU environment variable.

### TRICK_ICG_EXCLUDE

A colon separated list of directories to skip when processing header files.

It is possible to instruct ICG to skip entire directories using the environment variable TRICK_ICG_EXCLUDE. Set this variable to a colon separated list of directories which you wish ICG to bypass. This is useful when there is code which you do not wish Trick to have any knowledge of (i.e. you don’t need any of the parameters recorded or input processable).

### TRICK_LDFLAGS

TRICK_LDFLAGS include linker flags. TRICK_LDFLAGS is used when linking the simulation executable. It is rare to set this variable.

### TRICK_SFLAGS

TRICK_SFLAGS includes header file search directories and macro define variables. TRICK_SFLAGS is used when parsing the S_define file.

### TRICK_USER_LINK_LIBS

Additional library and library directories to include when linking a simulation.

An example of adding a library search path, a library to be searched for, and a full path library.

bash
```
export TRICK_USER_LINK_LIBS="-L/full/path/to/libs -lfile1 /another/path/to/a/libfile2.a"
```

[t]csh
```
setenv TRICK_USER_LINK_LIBS "-L/full/path/to/libs -lfile1 /another/path/to/a/libfile2.a"
```

### MAKEFLAGS

MAKEFLAGS is not a Trick environment variable. It is used with the GNU make utility. Invoking make with the -j flag allows make to compile more than one file simultaneously. Dramatic speedups in compiling can be achieved when using multiple processors.

```
UNIX Prompt> setenv MAKEFLAGS –j10
```

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