fstmap(1)

💖 fstmap — map an operation over an FST 💖

okay bestie, so you know fstmap(1) from User Commands? Yeah, that's the one. Sit down, hydrate, and let me tell you about it 🫶

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✨ SYNOPSIS ✨

fstmap [OPTIONS] [in.fst [out.fst]]

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🌸 DESCRIPTION 🌸

She takes an FST and applies an operation to each arc of it. That's it. That's the whole vibe. Every single arc gets the treatment, no arc left behind, periodt. 💅

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🎀 OPTIONS 🎀

quick lil housekeeping first: boolean options are chill like that — you can hand them either true or false as a value, or if you don't specify any value at all, they just implicitly go true. iconic behaviour honestly.

• --delta=VALUE — sets the comparison/quantization delta for a quantize operation. Default: 0.000976562.
• --fst_align[=BOOLEAN] — write FST data aligned where it makes sense to. Default: false.
• --fst_compat_symbols[=BOOLEAN] — require symbol tables to match when that's the appropriate move. Default: true.
• --fst_default_cache_gc[=BOOLEAN] — turns on garbage collection for the cache. Default: true.
• --fst_default_cache_gc_limit=N — the cache byte size that trips garbage collection and sends it off. Default: 1048576.
• --fst_error_fatal[=BOOLEAN] — if true, FST errors are fatal, no takebacks 😭. Otherwise the returned objects get flagged as bad — like, FSTs come back with the kError property set to true, and FST weights get set so that Member() returns false. Default: true.
• --fst_field_separator=STRING — sets which characters get used as the separator between printed fields. Default: " ".
• --fst_read_mode=STRING — sets the default file reading mode for mappable files, and it's either "read" or "map". Default: "read".
• --fst_verify_properties[=BOOLEAN] — verify the fst properties that TestProperties queries. Default: false.
• --fst_weight_parentheses=STRING — sets the characters that enclose the first weight of a printed composite weight (think pair weight, tuple weight, and derived classes) so nested composite weights do their I/O correctly. It must be size 0 (none) or 2 (an open and a close parenthesis). Default: no parentheses.
• --fst_weight_separator=CHARACTER — sets the character separator between printed composite weights. Default: comma.
• --help[=BOOLEAN] — show usage information. Default: false.
• --helpshort[=BOOLEAN] — show the brief usage information. Default: false.
• --map_type=TYPE — sets the map operation, and it's one of arc_sum, identity, input_epsilon, invert, output_epsilon, plus (which takes --weight), quantize (which takes --delta), rmweight, superfinal, times (which takes --weight), to_log, and to_log64. Default: identity.
• --save_relabel_ipairs=FILENAME — save the input relabel pairs to a file. Default: do not save.
• --save_relabel_opairs=FILENAME — save the output relabel pairs to a file. Default: do not save.
• --tmpdir=PATHNAME — sets the temporary directory to use. Default: /tmp.
• --v[=N] — sets the verbosity level. Default: 0.
• --weight=VALUE — sets the weight for a plus or times operation. Default: "".

girl. that is literally NINETEEN options. she is thorough and we respect her for it 👑

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👀 SEE ALSO 👀

the whole friend group, the squad, the entourage. go say hi:

fstarcsort(1), fstclosure(1), fstcompile(1), fstcompose(1), fstcompress(1), fstconcat(1), fstconnect(1), fstconvert(1), fstdeterminize(1), fstdifference(1), fstdisambiguate(1), fstdraw(1), fstencode(1), fstepsnormalize(1), fstequal(1), fstequivalent(1), fstinfo(1), fstintersect(1), fstinvert(1), fstisomorphic(1), fstlinear(1), fstloglinearapply(1), fstminimize(1), fstprint(1), fstproject(1), fstprune(1), fstpush(1), fstrandgen(1), fstrelabel(1), fstreplace(1), fstreverse(1), fstreweight(1), fstrmepsilon(1), fstshortestdistance(1), fstshortestpath(1), fstsymbols(1), fstsynchronize(1), fsttopsort(1), fstunion(1)

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and that's the whole page bestie!! this diva is OpenFst 1.8.5, dated Mar 2026 — go map some arcs and slay 💜✨🦋