15 Apr 2022

expandfile

This note describes expandfile, a simple command line program for expanding text templates. It is useful for many purposes, including enhancing HTML.

What expandfile Does

expandfile is a command line program that reads input files and writes output on standard output. (It runs on MacOS, Linux, or Windows. It is an open source Perl program, MIT license, available on GitHub.)

Characters in the input are copied to the output, except that when expandfile sees %[... something ...]% it expands it: that is, replaces the bracketed expression by its value in the output. expandfile keeps an internal table of named values.

Values come from variables set by input files, command line parameters, builtin functions, macro execution, external calls, and shell environment variables set by export.

One of the main uses for expandfile is translating an extension language for HTML called HTMX into regular HTML. expandfile enables you to

HTMX->expandfile->HTML

expandfile does not know the syntax of the text it is expanding. I have used it for many kinds of text transformation, including structured data to data transformations, e.g. CSV files => CSV files; CSV files => XML files; XML files => SQL files; SQL data => XML (e.g. sitemaps); SQL data => Procmail control files; SQL data => GraphViz input.

Command Usage

NAME

expandfile -- expand a template file

SYNOPSIS

expandfile [var=value]... file...

DESCRIPTION

expandfile reads template files and writes out text to standard output with variables and builtin functions expanded.

If a filename is specified as "-", standard input will be read.

You can optionally specify variable bindings on the command line in the format varname=value.

I usually make configuration files consisting of %[*set]% commands for site parameters, and provide them as the first filenames on the command line.

How To Use expandfile

With expandfile installed, you can type the command line

  expandfile template.htmx > template.html

to expand template.htmx and write its output into the file template.html.

expandfile doesn't know the syntax of HTML. It just sees character input and writes character output.

I rarely type expandfile on a command line; usually I invoke it in scripts that expand template source files into object files. For example, most HTML files on my websites are updated by the make utility, driven by a Makefile that invokes expandfile to expand a source template if the corresponding object file is out of date. See Using Unix tools with expandfile.

File Suffixes

Files with any suffix can be used as input or output files with expandfile: the program doesn't care. You can call your files whatever you wish. I use a set of conventions to remind myself of what files contain:

Use whatever file suffix helps you organize your source.

Variables

expandfile has an internal table of variables. Variables have names and values. A variable's name should not be blank. Letters, digits, and "()_+-" are allowed in variable names. (expandfile prints a warning if a variable name is all digits, because this is often an error.) Values are strings of characters, of any length. A variable that has never been set has a value that is the same as a variable with a zero length string value.

When expandfile is invoked, it starts with an empty variable table. The value of a variable is set by

If expandfile does not find a table entry for a variable name, it looks for a shell environment variable with that name (set by the export command), and if the variable is found, uses its value. If neither the internal table nor the shell environment supply a value, the value is an empty string.

expandfile builtin functions that set a variable require a & character in front of the variable name, to make it clear that the function will modify the value. If you leave the character out, a warning is printed.

When expandfile exits, the variable table's contents are discarded.

Expansion

Examples of expandfile's expansion are:

Expandfile algorithm

  1. Create an empty symbol table and initialize setup variables like date
  2. Read the input file into memory.
  3. Pass 1: invoke expandblocks to scan the memory copy for *block constructs. For each block,
    1. Note the block name and the ending regex.
    2. Copy the block conents and store them in the symbol table under the name.
    3. If the block already exists, append the contents to the end.
    4. Remove the block construct and contents from the memory copy.
  4. Pass 2: Call expandstring on the memory copy to
    1. Replace Multics formatting constructs if _xf_expand_multics is set and database parameters are defined.
      • Constructs like {[tag anchor]} that look up a tag in Multics database tables and create HTML links (4 variants)
      • Constructs like {:...:} that apply defined SPAN classes to text strings (4 variants)
    2. Replace %[*builtin...]% function calls with their values.
    3. Replace %[...]% variable references with their values.
  5. Write the expanded memory copy out to standard output.

HTMX Language

expandfile was originally written in Perl, and inherits some Perl semantics, like the equivalence of an unset variable and an empty string.

Stream Processing

expandfile reads its input and writes output. When reading input, the character \ is an escape character that is removed and removes the special meaning from the following character. Use "\\" to output "\". As described above, expandfile replaces named variables inside %[...]% by their values, and executes builtin functions like %[*builtin...]% that may take arguments, and may or may not output values.

Values in Argument Lists

Inside %[ ... ]%, literal values are preceded by = in order to distinguish them from variable names. For example, %[*set,&foo,=1]%.

expandfile prints a warning if it encounters a variable name that is all digits, because this may be an incorrectly formatted literal.

A string surrounded by double quote characters in a literal value prevents the interpretation of special characters, and is replaced by the contents without the quotes. Use quotes if the literal contains special characters such as , or %. To include a double quote character in a literal value, precede it with a backslash, e.g. \".

For example, the value of %[=say "hello \"world\"!"]% is say hello "world"!.

The literal value 14 can be expressed as =14 or ="14". Usually the second form is clearer.

Example:
If variable mike has the value nancy and variable nancy has the value 14, then
%[*set,&fred,="%[mike]%"]% will set variable fred's value to the six character string %[mike]%,
because the quotes prevent expansion of the inner expression.

Outside of %[ ... ]%, double quotes are just characters, and expandfile just copies them. (expandfile treats single quotes as ordinary characters.)

Values and Types

Variable values are character strings. They can be zero length, i.e. empty. A reference to a variable that was never set is not an error: the value returned is an empty string.

Some operations perform arithmetic operations on values, using Perl semantics. Addition, subtraction, and so forth are defined for values that contain digits only.

Example: (reference to a variable containing a value)
If variable nancy has the value 14 then
%[*set,&fred,nancy]% will set variable fred's value to 14.

Example:
If variable carol has the value aaaa then
%[*increment,&carol,=1]% will set carol's value to 1
because Perl addition of an alphabetic string and an integer tries to convert aaaa to an integer and gets a value of zero. This is not an error.

Nested Brackets

If expressions contain nested %[...]% sequences, the innermost set is expanded first.

Example:
If mike has the value nancy and nancy has the value 14, then
%[*set,&fred,%[mike]%]% will set fred's value to 14.
%[*set,&fred,=%[mike]%]% will set fred's value to nancy.

Builtin Functions

There are 37 builtin functions. They are pretty simple, mostly less than 10 lines of Perl each.

Some builtin functions write text to the output expansion; other builtins only change variables or cause other side effects; some do both.

Each builtin is briefly explained. See Expandfile Tutorial for more examples of many of these functions. A Builtin Summary table is provided below.

Tutorial example: Quoting, Constants, and Escaping.

Alphabetical List of builtins

%[** ....]%

Contains a comment.

Outputs nothing.

Example:
%[** this is a remark **]%.

%[*bindcsv,=file_or_url(in)]%

Read CSV file file_or_url and set variables.

Outputs nothing.

Fetch the contents of the specified file, local or remote, and treat it as a two-line file CSV file. (RFC-4180 defines this format. expandfile allows NL, CR, or CRLF line terminations, but does not support quoted line separators.) The first line is a comma separated list of variable names. The second line is a comma separated list of variable values. Bind each variable name to its corresponding value.

The variable _xf_colnames is set to a space separated list of column names bound by the query.

Example:
%[*bindcsv,=inputfile.csv]%

The *bindcsv builtin will not set variables whose names begin with underscore or period. A warning will be printed. If the = sign is omitted before the name of the input file or URL, a warning is printed.

Be careful about security if you read external values from the Internet and expand them. Sanitize your values before expanding.

%[*block,&blockname(out),regex(in)]%

Set blockname to unexpanded lines until regex.

Outputs nothing.

Read input lines following this command until a line matching the regular expression regex is found. For regex, use something like "^EOF$". Sets the value of variable blockname to all of the lines read, and removes them from the input. Text in %[...]% is copied with its brackets without expansion into blockname: when the block is expanded later these constructs will be processed. Specifying multiple blocks with the same blockname will append content to the block. The *block builtin should be used alone on a line.

This construct is used to set up a variable that can be expanded later, or expanded many times as an iterator, or called as a macro with *callv.

Example:
%[*block,&iterblock,^END]%
<tr><td>%[table1.name]%</td><td>%[table1.addr]%</td></tr>
END

Tutorial example:*block.

%[*callv,block(in),args...(in)]%

Expand block with arguments (subroutine call).

Outputs whatever is output by expanding block.

  1. Save all the variables param1,param2,param3,....
  2. Assign each variable param1=arg1,param2=arg2,param3=arg3,...
  3. Set _xf_n_callv_args to the number of arguments
  4. Expand block block, which will refer to param1 and so on.
  5. Restore all the variables param1,param2,param3,....

Use the *block builtin to define subroutine blocks, or use *include to load macro libraries. See Expandfile Macros for more about macro calls. The saving and restoring means that one block can invoke another block without arguments getting mixed up.

If *callv is called with an empty block, a warning is printed. (The first argument to *callv should not be quoted, since it is a block name.)

Example:
%[*callv,gettwodigit,month]%

See Macros in expandfile for more information on macros.

Tutorial example: macros and *callv.
%[*concat,&result(inout),valarg(in)...]%

Concatenate the values of each valarg onto result.

Outputs nothing, rewrites first argument.

Example:
%[*concat,&line,cityname,=", ",statename]%

%[*csvloop,&result(out),iter_block(in),=filename(in)]%

Set result to concatenated expansions of iter_block for each data row in filename.

Outputs nothing.

filename is an ASCII text file in CSV (comma separated values) format, like those produced by spreadsheet programs. RFC-4180 defines this format. (The file may be gzipped.)

The first row in the file is a heading row containing variable names for each column.

For each subsequent row, bind the variables in the symbol table using names from the heading row like colname1, and then expand iter_block, which can refer to these bound variables. Append the result of the expansion to result.

If the CSV file is missing, expandfile exits with an error message. (Maybe it should keep going, or there should be a switch saying what to do.)

The variable _xf_nrows is set to the count of rows found by the query.

The variable _xf_colnames is set to a space separated list of column names bound by the query.

Example:
%[*csvloop,&report,btrr_iter,=btrr.csv]%

Tutorial example: *csvloop.

%[*decrement,&variable(inout),value(in)]%

Decrement variable's contents.

Outputs nothing, rewrites first argument.

Uses Perl semantics.

Example:
%[*decrement,&openfiles,="1"]%

%[*dirloop,&result(out),iter_block(in),=dir(in),starrex(in)]%

Set result to concatenated expansions of iter_block for each entry in dir matching starrex.

Outputs nothing.

Operates on each file-system file in a directory dirpath whose name matches starrex. For each file, do a Unix stat() operation on the file and bind variables to the values of the file attributes, and then expand iter_block, which can refer to these variables. Append the result of the expansion to result.

The variables bound are

file_namename of the file
file_type'f' for file, 'd' for directory, 'l' for link
file_devdevice number
file_inoinode number
file_modemode in Unix character format, e.g. "rwx--x---"
file_nlinknumber of hardlinks to the file
file_uidnumeric file owner userid
file_gidnumeric file owner groupid
file_rdevrdev (for special files)
file_sizesize in bytes
file_atimelast access time
file_mtimelast mod time
file_ctimeinode change time
file_blksizepreferred block size
file_blocksallocated blocks
file_secmtime seconds (2 digits)
file_minmtime minutes (2 digits)
file_hourmtime hour (2 digits)
file_mdaymtime day of month (2 digits)
file_monmtime month (2 digits)
file_yearmtime year (2 digits)
file_wdaymtime day of week (0-6, Sunday is 0))
file_ydaymtime day of year
file_isdst1 if mtime is DST
file_datemodmtime in the format "mm/dd/yy hh:mm"
file_modshortmtime in the format "mm/dd/yy"
file_sizekfile size in K
file_ageage in days

The variable _xf_nrows is set to the count of files found.

Example:
%[*dirloop,&content,format_one_file,=".",="."]%

Tutorial example: *dirloop.

%[*dump]%

Display the contents of all variables in the symbol table.

Outputs one line per defined variable.

Example:
%[*dump]%

%[*exit]%

Abort expandfile execution.

Outputs nothing.

Example:
%[*exit]%

%[*expand,var(in)]%

Expand var including variable and builtin references.

Outputs value of var, expanded.

var may contain variable names and builtin invocations in %[... ]%. Nested expansions are possible if the variable invokes %[*expand,...]% or other builtins.

Outputs the value of expanding var. If var contains %[ ... something ...]% constructs, they will be expanded.

Example: output the contents of a variable
%[*expand,footnote_separator]%.

Example: output the contents of a variable whose name depends on another variable
%[*expand,footnote_%[ftn]%]%.

%[*expandv,&result(out),var(in)]%

Set result to expansion of var including variable and builtin references.

Outputs nothing.

var may contain variable names and builtin invocations in %[... ]%. Nested expansions are possible if the variable invokes %[*expand,...]% or other builtins.

Sets its first argument to the expansion of var. Outputs nothing. If var contains %[ ... something ...]% constructs, they will be expanded.

Example:
%[*expandv,&formatted_name,convert_cityname]%

%[*fappend,=filename(in),value(in)...]%

Append concatenated value args to the contents of filename.

Outputs nothing.

Example:
%[*fappend,=tracefile.txt,timestamp,=" ",traceoutput]%

%[*format,&result(out),fmtstring(in),vars...(in)]%

Replace placeholders of the form "$1" .. "$n" in fmtstring with values of the vars.

Outputs nothing.

Example: combine cityname and statename:
%[*format,&line,="$1, $2",cityname,statename]%

Example: Generate an HTML IMG tag:
%[*format,&imgtag,="<img src=\"$1\" width=\"$2\" height=\"$3\">",filename,height,width]%

Example: Generate GraphViz (dot) input:
%[*if,ne,t.st,="invis",*format,&x,="$1 -> $2 [xlabel=\"$3\",style=\"$4\",color=\"$5\"];\n",y.n1,y.n2,y.b,y.e,t.o]%

The second example statement was used in an iterator block in an application that produced a block diagram from an SQL file.

%[*fread,&result(out),=filename(in)]%

Read the contents of filename into result.

Outputs nothing.

If the input file is not found, set content to the empty string. Does not expand blocks, builtins, or variables.

Sets its first argument. Outputs nothing.

Example:
%[*fread,&pienumber,=pienumberfile]%

%[*fwrite,=filename(in),value(in)...]%

Rewrite filename with concatenated value args.

Outputs nothing.

Replaces any previous contents of filename.

Example:
%[*fwrite,=pienumberfile,counter%

%[*htmlescape,value(in)...]%

Output the HTML-escaped value of concatenated value args.

Outputs the escaped string.

For instance, html-escaping "<fred>" yields "&lt;fred&gt;".

Example:
%[*htmlescape,filename]%

%[*if,relop(in),v1(in),v2(in),statement...(in)]%

if (v1 relop v2), expand statement.

Outputs If condition is true, whatever the contained statement outputs.

Perform the comparison v1 relop v2 and if it is TRUE, expand statement. statement can be any set of HTMX evaluations, including more "if" builtins. relop is the name of a comparison operator. The supported operators are:

  • eq numeric equality
  • ne numeric inequality
  • gt numeric greater-than
  • lt numeric less-than
  • ge numeric greater-equal
  • le numeric less-equal
  • =~ regular expression equality
  • !~ regular expression equality
  • teq string equality
  • tne string inequality
  • tgt string greater-than
  • tlt string less-than
  • eqlc string equality, case independent
  • nelc string equality, case independent

Outputs whatever statement outputs.

Example:
%[*if,eq,city,="Chicago",*set,&airport,="ORD"]%.

Nested *if statements:
%[*if,ne,gnm,param1,*if,ne,tnms,="",*callv,rec_grpname2grpid,param1]%

Another nested *if statement, setting up a format string for the *format builtin:
%[*if,gt,x3,param3,*if,gt,x1,=0,*set,&fmt,=" <span class="inred">($1$2%)</a>"]%

Tutorial example: *if.

%[*include,=filename(in)]%

Output the expanded content of filename.

Outputs filename content, expanded.

Expands blocks, builtins, and variables.

If the file is not found, this is a fatal error and expandfile exits.

Example:
%[*include,=page-wrapper.htmi]%.

Tutorial example: *include.

%[*includeraw,=filename(in)]%

Output the content of filename, unexpanded.

Outputs filename content, unexpanded.

Does not expand blocks, builtins, or variables.

If the file is not found, this is a fatal error and expandfile exits.

Example:
%[*includeraw,=data_table.txt]%.

%[*increment,&variable(inout),value(in)]%

Increment variable's contents.

Outputs nothing, rewrites first argument.

Add the value in value to the value in result and store the result into result. Uses Perl semantics.

Example:
%[*increment,&pageno,="1"]%

%[*ncopies,&result(out),value(in),n(in)]%

Set result to n copies of value.

Outputs nothing.

Concatenate n copies of the value in value and store the result into result.

Example:
%[*ncopies,&amt,="*",width]%

%[*onchange,var(in),*statement(in)]%

Execute statement when value of var changes.

Outputs whatever is output by contained statements.

If the value of var has changed, execute the statement. This builtin is useful in iterators invoked by *sqlloop, *csvloop, *xmlloop, *dirloop, and *csvloop.

Example:
%[*onchange,x,*callv,wrap,x,="&nbsp;&nbsp;&nbsp;&nbsp;<dt>",="</dt>\\n"]%
outputs a line that surrounds the value of x with <dt> and </dt> if x is nonempty and changed. (See the definition of the wrap macro in Macros in expandfile).

%[*onnochange,var(in),*statement(in)]%

Execute statement when value of var is unchanged.

Outputs whatever is output by contained statements.

If the value of var has NOT changed, execute the statement. This builtin is useful in iterators invoked by *sqlloop, *csvloop, *xmlloop, *dirloop, and *csvloop.

If an iterator block uses both *onchange and *onnochange, put the onnochange call first.

Example:
%[*onnochange,x,*increment,&titles,=1]%

%[*popssv,&result(out),&ssv(inout)]%

Set result to first element of ssv, and ssv to the remainder.

Outputs nothing, rewrites second argument.

Variable ssv should contain a list of strings separated by a separator character whose value is in _xf_ssvsep. (By default the character is a space -- SSV means "space separated values.") Remove the leftmost element of ssv, store it in result, and rewrite ssv with the rest. If ssv contains only one element, store it in result and leave ssv empty.

See also the *ssvloop builtin.

Example:
%[*popssv,&next_player,&jersey_numbers]%]%

Tutorial example: SSVs.

%[*product,&var(inout),value(in)]%

Multiply result by value.

Outputs nothing, rewrites first argument.

Multiply the value in result by the value in value and store the result in result.

Example:
%[*product,&mins,hours,=60]%

%[*quotient,&result(out),dividend(in),divisor(in)]%

Set result to dividend divided by divisor.

Outputs nothing.

Divide the value in dividend by the value in divisor and store the result in result. Discard the fractional part. If divide by zero is attempted, the result is 0.

Example:
%[*quotient,&cows,hooves,=4]%

%[*quotientrounded,&result(out),dividend(in),divisor(in)]%

Set result to dividend divided by divisor, rounded.

Outputs nothing.

Divide the value in dividend by the value in divisor and store the result in result, rounded to the nearest integer. That is, compute int((dividend / divisor) + 0.5); If divide by zero is attempted, the result is 0.

Example:
%[*quotientrounded,&cows,hooves,=4]%

%[*scale,&result(out),n(in),range(in),base(in)]%

Set result to int(((n*base)/range)+0.5).

Outputs nothing.

Compute int(((n*base)/range)+0.5) and store the result in result. range is the maximum value for the variable n and base is the maximum scaled value.

For example, if you are drawing an HTML horizontal bar graph that will be 500 pixels wide (the base), of variables that run from 0 to 1000 units, then each graph pixel will represent 2 units.

Example: Computing the width of a bar in the graph:
%[*scale,&barwidth_pixels,wtdayhist.dhits,.maxdhits,=500]%
<img src="redpixel.gif" height="10" width="%[barwidth_pixels]%">
This uses up to 500 pixels to display a graph bar whose longest bar represents .maxdhits.

%[*set,&result(out),valarg(in)...]%

Set result to concatenated valarg arguments.

Outputs nothing.

If a value begins with an = then it is a literal value. Otherwise it is a variable name whose value is used.

Example: set a variable to a constant string.
%[*set,&title,="Expandfile Usage"]%.

Example: set a variable to the value of another variable.
%[*set,&title,datafield]%.

Example: set a variable to the concatenated values of several arguments. (quote is a builtin value.)
%[*set,&htt,="https://multicians.org/thvv/htmx/expandfile.html"]%
%[*set,&anchorstring,="Expandfile"]%
%[*set,&test6,="<a href=",quote,htt,quote,=">",anchorstring,="</a>"]%.

quote is a builtin variable whose value is a double quote character. I could have written ="\"" instead.

Tutorial example: *set.

%[*shell,&result(out),command(in)...]%

Execute shell command and set result to its output.

Outputs nothing.

The string sent to the command processor is the concatenation of the values of command arguments.

If multiple lines are returned, newline characters are replaced by the contents of _xf_ssvsep. The command output is stored in result.

Be careful about security if you execute shell commands based on user input.

You can write your own functions, or use Unix programs such as grep, sed, awk, or sh.

Several useful utility functions are supplied with expandfile.

Example: get the date modified of a file (*shell is called with one argument, which contains an expansion of the variable parm1)
%[*shell,&filed,=filemodshort %[param1]%.htmx]%

Example: get the age in days of the index file in a directory (note the concatenation of constants and variable values)
%[*shell,&xage,="filedaysold ",obj_dir,="/",param1,="/index.html"]%

Example: use perl to modify a disk file to remove the string "NAMESP:" everywhere (note that double-quote is preceded by \ inside a string)
%[*shell,&xout,="perl -pi -e \"s/NAMESP://g\" ",filenamevar]%

Example: invoke the mysql command to load a disk file containing MySQL statements (note that we don't quote the argument)
%[*shell,&xout,=mysql --execute \"source %[sqlloadfile]%\"]%

Example: invoke the curl command to download output from a web service API
%[*shell,&xout,=curl %[endpoint]%/%[cmd]% -X POST -d %[JSON_rq]% -H \"Content-type: application/json\" > xx.json]%

Performance was not a consideration in the design of the *shell builtin. Executing command lines this way is done by launching a fairly large shell process, and then launching additional processes for each command in the arguments to the shell. (I expand one template, sitemap.htmx, which invokes filemodshort and filesizek for each of over 1000 pages. There is a pause of 10 seconds or so when the template is expanded.)

Tutorial example: *shell.

%[*sqlloop,&result(out),iter_block(in),query(in)]%

Set result to concatenated expansions of iter_block for each row returned by MySQL query.

Outputs nothing.

Execute the MySQL query query, which returns a number of rows. Each row returns a set of variables. Bind the variables in the symbol table using names like table.varname1, and then expand iter_block, which will refer to these variables. Append the result of the expansion to result. (Because _xf_colnames is set before iter_block is expanded, the iterator need not know the complete schema of the database.)

The variable _xf_nrows is set to the count of rows found by the query.

The variable _xf_colnames is set to a space separated list of column names bound by the query.

Computed values such as COUNT that have no tablename are bound to names like .count.

The variables _xf_hostname, _xf_database, _xf_username, and _xf_password must be set up to point to the MySQL database server before sqlloop is invoked, or expandfile will exit with an error message.

Some database errors are retryable, for instance if the server goes down. sqlloop will retry these errors 10 times before exiting with an error.

If there is a fatal database or query error, expandfile exits with an error message.

If the query is empty, a warning will be printed and _xf_nrows will be set to 0. It is not an error for a query to return 0 rows, but a warning will be printed.

Example: generate a bar chart summarizing population by country name from table "s":
%[*sqlloop,&chartout,chart_iter,="SELECT country, COUNT(*) AS v FROM s WHERE fake=0 GROUP BY country"]%

To execute a query just to set a total, specify a variable for the loop output that you never use, and a null iterator, and refer to the query result, e.g.
%[*sqlloop,&junk,="",="SELECT COUNT(*) AS minors FROM tbl WHERE age < 21"]%
%[*set,&minorcount,%[.minors]%]%

Tutorial example: *sqlloop.

%[*ssvloop,&result(out),iter_block(in),ssv(in)]%

Set result to concatenated expansions of iter_block for each element of ssv.

Outputs nothing.

An SSV (space separated values) list is a variable value composed of tokens separated by the value in _xf_ssvsep (usually space).

Operate on each token in the SSV varname. For each token, bind _xf_ssvitem to the value (null tokens are skipped), and then expand iter_block, which can refer to _xf_ssvitem. Append the result of the expansion to result. This loop works on a copy of varname, so the input SSV is not changed.

The variable _xf_nssv is set to the count of tokens found in the SSV.

See also the *popssv builtin.

Example:
%[*ssvloop,&nextstorybody,nextstory-iter,filenamesbydate]%

Tutorial example: *ssvloop.

%[*subst,&var(inout),leftside(in),rightside(in)]%

Substitute right for left in var.

Outputs nothing, rewrites first argument.

Replace the value in result by the result of the Perl substitution s/left/right/ig. Slashes in left and right must be escaped -- use \\.

left can contain parenthesized patterns, as in Perl substitutions; these patterns can be referenced in right as \\1, \\2, etc.

Example: truncate a name to its first 40 characters
%[*subst,&name,="^(........................................).*$",="\\1"]%

Example: trim off the directory portions of a pathname
%[*subst,&pname,="^.*\\/",=""]%

Be careful about security if you read external values from the Internet and use them in arguments to *subst. Watch out for backticks.

%[*urlfetch,&result(out),url(in)]%

Set result to contents of url.

Outputs nothing.

Fetch the contents of the Internet URL url into result. If the target is not found, set content to the empty string. Does not expand variables or blocks.

Be careful about security if you read external values from the Internet and expand them. Sanitize your values before expanding. Watch out for %[]% and backticks.

Example:
%[*urlfetch,&contents,=%[_xf_ssvitem]%]%

%[*xmlloop,&result(out),iter_block(in),=filename(in),xpath(in)]%

Set result to concatenated expansions of iter_block for each XML item in filename matching xpath.

Outputs nothing.

filename is an ASCII text file in XML format. It may be gzipped.

Operate on each item the file as found by Xpath: if this argument is missing, the default is "/*/*". For each item found by the Xpath, the loop binds the values of sub-items "./*" and binds the values of attributes "./@*", and then expands iter_block, which will refer to these variables. Append the result of the expansion to result.

If no Xpath is provided, the outermost structure in the file should be something like <list> ... </list> and it should contain repeated items <item> ... </item> which in turn contain multiple fields like <person> ... </person> and <address> ... </address>. For each item, bind the values of fields in the symbol table using names like person.

The variable _xf_nxml is set to the count of items found by the query.

The variable _xf_xmlfields is set to a space separated list of variable names bound by the query.

If the XML file is empty or malformed, _xf_nxml is set to 0 and nothing is done. If the XML file is missing, expandfile exits with an error message. This is ugly: I should think of a better solution.

Example:
%[*xmlloop,&junk,iter_gacc,=gacc.xml,="*/computers/computer"]%

I use a simple Perl program called json2xml to translate JSON data (fetched from a web API) into XML data, which I then process with *xmlloop.

Tutorial example: *xmlloop.

%[*warn,args...(in)]%

Write args to STDERR.

Outputs nothing.

Write a warning message args... on STDERR.

Example:
%[*warn,No results for %[query]%]%

Builtin Summary

Some builtin functions write output to the output file. Others produce no output but instead change an argument variable. A few functions conditionally expand the rest of their arguments, so these produce output wherever their arguments direct.

Builtin functions that modify an argument use & before the variable name to remind you that the value will be modified. If you omit the &, expandfile prints a warning. Some builtins with & have in/out args, others are out.

BuiltinFunctionOutput
**Starts a commentnothing
*bindcsv,=file_or_url(in)Read CSV file file_or_url and set variablesnothing
*block,&blockname(out),regex(in)Set blockname to unexpanded lines until regexnothing
*callv,block(in),args...(in)Expand block with arguments (subroutine call)whatever is output by expanding block
*concat,&result(inout),valarg(in)...Concatenate the values of each valarg onto resultnothing, rewrites first argument
*csvloop,&result(out),iter_block(in),=filename(in)Set result to concatenated expansions of iter_block for each data row in filenamenothing
*decrement,&variable(inout),value(in)Decrement variable's contentsnothing, rewrites first argument
*dirloop,&result(out),iter_block(in),=dir(in),starrex(in)Set result to concatenated expansions of iter_block for each entry in dir matching starrexnothing
*dumpDisplay the contents of all variables in the symbol tableone line per defined variable
*exitAbort expandfile executionnothing
*expand,var(in)Expand var including variable and builtin referencesvalue of var, expanded
*expandv,&result(out),var(in)Set result to expansion of var including variable and builtin referencesnothing
*fappend,=filename(in),value(in)...Append concatenated value args to the contents of filenamenothing
*format,&result(out),fmtstring(in),vars...(in)Replace placeholders of the form "$1" .. "$n" in fmtstring with values of the varsnothing
*fread,&result(out),=filename(in)Read the contents of filename into resultnothing
*fwrite,=filename(in),value(in)...Rewrite filename with concatenated value argsnothing
*htmlescape,value(in)...Output the HTML-escaped value of concatenated value argsthe escaped string
*if,relop(in),v1(in),v2(in),statement...(in)if (v1 relop v2), expand statementIf condition is true, whatever the contained statement outputs
*include,=filename(in)Output the expanded content of filenamefilename content, expanded
*includeraw,=filename(in)Output the content of filename, unexpandedfilename content, unexpanded
*increment,&variable(inout),value(in)Increment variable's contentsnothing, rewrites first argument
*ncopies,&result(out),value(in),n(in)Set result to n copies of valuenothing
*onchange,var(in),*statement(in)Execute statement when value of var changeswhatever is output by contained statements
*onnochange,var(in),*statement(in)Execute statement when value of var is unchangedwhatever is output by contained statements
*popssv,&result(out),&ssv(inout)Set result to first element of ssv, and ssv to the remaindernothing, rewrites second argument
*product,&var(inout),value(in)Multiply result by valuenothing, rewrites first argument
*quotient,&result(out),dividend(in),divisor(in)Set result to dividend divided by divisornothing
*quotientrounded,&result(out),dividend(in),divisor(in)Set result to dividend divided by divisor, roundednothing
*scale,&result(out),n(in),range(in),base(in)Set result to int(((n*base)/range)+0.5)nothing
*set,&result(out),valarg(in)...Set result to concatenated valarg argumentsnothing
*shell,&result(out),command(in)...Execute shell command and set result to its outputnothing
*sqlloop,&result(out),iter_block(in),query(in)Set result to concatenated expansions of iter_block for each row returned by MySQL querynothing
*ssvloop,&result(out),iter_block(in),ssv(in)Set result to concatenated expansions of iter_block for each element of ssvnothing
*subst,&var(inout),leftside(in),rightside(in)Substitute right for left in varnothing, rewrites first argument
*urlfetch,&result(out),url(in)Set result to contents of urlnothing
*xmlloop,&result(out),iter_block(in),=filename(in),xpath(in)Set result to concatenated expansions of iter_block for each XML item in filename matching xpathnothing
*warn,args...(in)Write args to STDERRnothing
37 builtins

(If I had it to do over, I might make all functions take an output argument, and have none of them write to the output.)

Builtin Values

These values are set up by expandfile when it is invoked. Probably a bad idea to store into any of these. (Example value in parentheses.)

%[year]%year (2022)
%[prevyear]%previous year (2021)
%[day]%day (15)
%[month]%month (Apr)
%[prevmonth]%previous month (Mar)
%[monthx]%numeric month (04)
%[hour]%hour (16)
%[min]%min (27)
%[date]%date in text format (15 Apr 2022)
%[timestamp]%timestamp (2022-04-15 16:27)
%[pct]%percent (%)
%[lbkt]%left bracket ([)
%[rbkt]%right bracket (])
%[lbrace]%left brace ({)
%[rbrace]%right brace (})
%[quote]%double quote (")
%[_xf_currentfilename]%current file name being expanded (expandfile.htmx>xfwrapper.htmi)
%[_xf_version]%version of expandfile (6.03)

Special Values

%[_xf_expand_multics]%user configIf nonblank, enable Multics expansions.
%[_xf_debug]%user configIf nonblank, enable warnings about unset variables.
%[_xf_tracebind]%user configIf set to a nonblank value, causes *set, *block, *sqlloop, *csvloop, *xmlloop, *dirloop, and *csvloop
to print a message on STDERR when they bind a value to a variable.
%[_xf_ssvsep]%user configSeparator between elements of a Space Separated Values list. Default is " ".
%[_xf_nssv]%Set by *ssvloopNumber of elements processed.
%[_xf_ssvitem]%Set by *ssvloopCurrent item inside an iterator block being expanded.
%[_xf_nrows]%Set by *sqlloop, *csvloop, *dirloopRows read
%[_xf_colnames]%Set by *sqlloop, *csvloop, and bindcsvSSV of column names bound.
%[_xf_xmlfields]%Set by *xmlloopSSV of XML item names bound.
%[_xf_nxml]%Set by *xmlloopNumber of XML items read.
%[_xf_n_callv_args]%Set by *callvNumber of 'paramN' args to macro.
%[_xf_currentfilename]%Set by expandfileName of file currently being read.

Macro Libraries

One way to extend the function of expandfile is to write macros. As mentioned above, you can define these macros using *block, and expand them using *callv. If you decide to use the macros for more than one file, it is natural to move the macros to a separate file (I use the file suffix .htmi meaning "HTMX Include") and incorporate them into the files that invoke them with a command like %[*include,=macro_lib.htmi]%.

A library of macros called htmxlib.htmi is provided with expandfile. It contains macros you can use or adapt to your own needs.

For example, one macro is getimgdiv, which can generate HTML IMG tags with the WIDTH and HEIGHT of a graphic. The IMG tag will use SRCSET when a graphic image is represented in multiple sizes, to show the optimum image for the viewer's screen resolution. (see High DPI Pictures.) Call it by

  %[*callv,getimgdiv,path,target,alttag,titletag,class,caption]%

See "Macros in Expandfile" for more information.

Multics Mode Formatting Expansions

expandfile also expands nine special text formatting macros developed to simplify the source of the multicians.org website, its first application. See "expandfile Features for Multicians.org" for more information. These macros are applied to all text, whether inside %[ ... ]% or not.

To prevent these macros from being expanded and interpret them as literal text, precede them by a backslash (\). For example, \{: ... :}, \{\= ... =}, \{\+ ... +}, \{\- ... -}, \{\* ... *}, \{\[ ... ]}, \{\{ ... }}, \{\! ... !}, \{\@ ... @} .

How To Install expandfile

Basically, you set up some OS tools and prerequisite software, and then download expandfile and its Perl module files and some auxiliary files from github.com/thvv/expandfile, and install them on your search path.

Macintosh
The Mac Terminal program gives you a Unix command shell. Install Apple Xcode to get command line tools such as make and rsync. You may wish to install Mac toolsand Perl from homebrew to get more up-to-date versions (see below).
  1. install Apple Xcode (free from Apple) from the App Store
  2. install command line tools from the Xcode menu
  3. Set environment variables so your /bin is searched (see below)
  4. install any programs and libraries you need from MacPorts or homebrew
  5. Install MySQL from Oracle (see below)
  6. Install Perl (see below).
  7. Install CPAN modules needed by expandfile (see below)
  8. Visit the expandfile github repository and clone the repository
  9. Copy expandfile and its Perl modules to your /bin
Linux and Unix
Unix distributions come with some command line tools already installed. You may need to use your distribution's package manager to install additional programming tools in order to get make, rsync, and so on.
  1. Set environment variables so your /bin is searched (see below)
  2. install programs and libraries you need from your package manager, including MySQL
  3. Install Perl if it is not already installed
  4. Install CPAN modules needed by expandfile (see below)
  5. Visit the expandfile github repository and clone the repository
  6. Copy expandfile and its Perl modules to your /bin
Windows
Use an environment like MINGW, MSYS2, or Cygwin to install a command shell, Perl, MySQL, CPAN Perl modules, and then use the Unix instructions. (I haven't tried this in a long time. I have never tried PowerShell.)

Set up a bin directory and Set Environment Variables

Create a directory called /bin in your home directory, and then add it to your PATH environment variable, by issuing the following commands in a Terminal or shell window (assuming your shell is bash):

  cd $HOME
  mkdir bin
  echo "export PATH=$HOME/bin:$PATH" >> .bash_profile
  . .bash_profile

Set Values in Your Shell Environment

Arrange to set configuration values for Perl in your shell environment. Linux and Windows will be similar. For example, if you are using Perl 5.26 on a 64-bit Mac using Homebrew, you would set up

  export VERSIONER_PERL_PREFER_32_BIT="no"
  export PERL5LIB=/Users/thvv/bin:/usr/local/lib/perl5/5.34.0:/usr/local/Cellar/perl/5.34.0/lib/perl5/site_perl/5.34.0
  export PERL_LOCAL_LIB_ROOT="/usr/local/lib/perl5/5.34"
  export PERL_MB_OPT="--install_base "/usr/local/lib/perl5/5.34""
  export PERL_MM_OPT="INSTALL_BASE=/usr/local/lib/perl5/5.34"

in your .bash_profile.

Install Perl

expandfile is written in the Perl language. Your computer must have Perl installed, and your Perl library has to have a few modules installed. Macs and most Linux systems come with Perl, with the library set up. To check if Perl is installed and what version it is, type perl -v; my computer says

  This is perl 5, version 34, subversion 0 (v5.34.0) built for darwin-thread-multi-2level

For Macintosh on of macOS Big Sur, I install Perl with Homebrew. Once Homebrew is installed, you can add packages such as ImageMagick. See https://formyfriendswithmacs.com/homebrew.html.

expandfile and its helper programs in Perl have a "shebang" line of #!/usr/local/bin/perl, which selects which version of Perl will be executed when the shell executes a command.
On my Mac, Homebrew sets up /usr/local/bin/perl.
On Linux, I link /usr/local/bin/perl to /usr/bin/perl.

Ensure that your shell environment variable PERL5LIB points to your $HOME/bin and to libraries for the same version of Perl.
On my Mac using Big Sur, my PERL5LIB is /Users/thvv/bin:/usr/local/lib/perl5/5.34.0:/usr/local/Cellar/perl/5.34.0/lib/perl5/site_perl/5.34.0.
On Linux, my PERL5LIB is $HOME/bin:/usr/local/lib/perl5.

Set your shell environment variables VERSIONER_PERL_PREFER_32_BIT, PERL_LOCAL_LIB_ROOT, PERL_MB_OP, and PERL_MM_OPT for your local environment.

Install MySQL

expandfile needs MySQL even if you never invoke *sqlloop, because it loads the CPAN module DBD::mysql, which won't install unless MySQL is available. (I am looking into a way to remove this dependency.) There is no standard Perl way to only load a module if it is needed at runtime. Download and install MySQL.

To configure MySQL, define a "root" user and password, and create a database. (Installing mysql may generate a temporary root password you have to change. This seems to be different for each MySQL release.) Then set up the file .my.cnf in your home directory so that you can access the database without giving your password every time. You'll want to set up a configuration file like config.htmi that sets values for expandfile, so that your programs don't have to have the credentials baked in.

"On Unix, MySQL programs treat the host name localhost specially, in a way that is likely different from what you expect compared to other network-based programs. For connections to localhost, MySQL programs attempt to connect to the local server by using a Unix socket file. This occurs even if a --port or -P option is given to specify a port number. To ensure that the client makes a TCP/IP connection to the local server, use --host or -h to specify a host name value of 127.0.0.1, or the IP address or name of the local server. You can also specify the connection protocol explicitly, even for localhost, by using the --protocol=TCP option."

Install Perl Modules from CPAN

Expandfile depends on having several Perl library modules installed. If these are not installed already, install them using CPAN:

ModuleDescription
LWP::SimpleSupport for *urlfetch and *bindcsv
Term::ANSIColorSupport for error messages
DBI and DBD::mysqlSupport for *sqlloop
XML::LibXMLSupport for *xmlloop
XML::SimpleIf you use json2xml
JSONIf you use json2xml

Install and configure cpan if it is not installed, and then install these modules using the cpan command. e.g.

     sudo -H cpan install XML::LibXML

On a Mac, see https://formyfriendswithmacs.com/cpan-sl.html.

On Fedora Linux, I found that XML::Simple::get was failing on https URLs. A little test got the message 501 Protocol scheme 'https' is not supported (LWP::Protocol::https not installed) at t.pl line 8. Trying to install LWP::Protocol::https failed with CPAN errors. I had to manually install Net::SSLeay to get it to work.

Download expandfile from Git

Visit https://github.com/thvv/expandfile in your browser.
Click the green "Code" button.
Choose "Clone" or "Download ZIP."
Move the downloaded files into your bin directory.

This will give you the following files in your /bin directory:

FilenameDescription
expandfileCommand line program
expandfile.pmInternals of expandfile
readbindsql.pmInternals of expandfile for *sqlloop
readbindxml.pmInternals of expandfile for *xmlloop

You also get some useful helper programs in Perl, for invocation by the *shell builtin.

FilenameDescriptionExample
checknonemptyexit with error if arg is missing or empty; used in Makefiles
csv2sql.htmtHTMX macro to convert a CSV file to a SQL table declaration--
filedaysoldreturn file age%[*shell,&x,=filedaysold example-page.htmx]%
159
filemodisoreturn file mod date as yyyy-mm-dd/td>%[*shell,&x,=filemodiso example-page.htmx]%
2021-11-07
filemodshortreturn file mod date as mm/dd/yy%[*shell,&x,=filemodshort example-page.htmx]%
11/07/21
filemodyearreturn year of file modification%[*shell,&x,=filemodyear example-page.htmx]%
2021
filesizekreturn file size%[*shell,&x,=filesizek example-page.htmx]%
1
firstletterreturn first letter of a string%[*shell,&x,=firstletter abcdef]%
A
firstofnextmonthreturn date of the first of next month%[*shell,&x,=firstofnextmonth]%
01 May 2022 00:00:00 GMT
fmtnumreturn a number formatted with commas, as a file size, or as a date%[*shell,&x,=fmtnum 1234567 num]%
1,234,567
fmtsqlreturn a string formatted so that it can be input safely to mysql%[*shell,&x,=fmtsql "isn't"]%
isn''t
gifsize2return image size: used by getimgdiv macro%[*shell,&x,=gifsize2 tinymultics.gif]%
16 16 tinymultics.gif
gifsizedisplay length of a graphic%[*shell,&x,=gifsize tinymultics.gif]%
"tinymultics.gif" width="16" height="16"
gth2xshell script to generate 150x150 thumbnails (uses ImageMagick convert)--
gthumbshell script to generate thumbnails (uses ImageMagick convert)--
htmxlib.htmimacro library--
lowercasereturn lowercase version of a string%[*shell,&x,=lowercase Boston]%
boston
nargsreturn the number of args%[*shell,&x,=nargs 1 2 3]%
3
padstringpad a text field with blanks to a given width%[*shell,&x,=padstring 6 "X"]%
"X     "
padleftpad a text field with blanks on the left to a given width%[*shell,&x,=padleft 6 "Q"]%
"     Q"
uppercasereturn uppercase version of a string%[*shell,&x,=uppercase hello]%
HELLO
xml2sqltranslate a simple XML file into a SQL table declaration--

You can write other little commands to invoke with %[*shell]% to extend HTMX, as shell scripts or programs in C, Perl, Python, and so on, and place them in your /bin directory. You can also invoke Unix commands with %[*shell]%, such as date, grep, sed, awk, cut, and sort.

Try it out

You should be able to type the command

  expandfile

and get a USAGE message, and no errors. This will show that expandfile and its needed Perl modules are correctly installed.

Type the command

  expandfile foo

where foo is a plain text file without %[...]% or \ and you should get the same output as the contents of foo.

Then try some of the examples in the expandfile Tutorial.