Consistently refer to STDIN/STDOUT in man pages in this way.

man/osmium-check-refs.md

@@ -33,7 +33,7 @@ change files.
 # OPTIONS
 
 -i, --show-ids
-:   Print all missing IDs to *stdout*. If you don't give this option, only a
+:   Print all missing IDs to STDOUT. If you don't give this option, only a
     summary is shown.
 
 -r, --check-relations

man/osmium-diff.md

@@ -61,7 +61,7 @@ None of the output formats print the headers of the input files.
 :   See the **OUTPUT FORMATS** section.
 
 -o, --output=FILE
-:   Name of the output file. Default is '-' (*stdout*).
+:   Name of the output file. Default is '-' (STDOUT).
 
 -O, --overwrite
 :   Allow an existing output file to be overwritten. Normally **osmium** will

man/osmium-file-formats.md

@@ -22,8 +22,8 @@ In addition files in all formats except PBF can be compressed using *gzip* or
 
 Which format a file has is usually autodetected from the file name suffix.
 
-If this doesn't work, either because you are reading from stdin or writing to
-stdout, or because you have an unusual file name, you have to set the format
+If this doesn't work, either because you are reading from STDIN or writing to
+STDOUT, or because you have an unusual file name, you have to set the format
 manually. You can also set the format manually if you want to specify special
 format options.
 

man/osmium-fileinfo.md

@@ -74,7 +74,7 @@ The following variables are available:
     file.name - STRING
     file.format - STRING: XML|PBF
     file.compression - STRING: none|bzip2|gzip
-    file.size - INTEGER (0 for stdout)
+    file.size - INTEGER (always 0 when reading from STDIN)
     header.with_history - BOOL (yes|no)
     header.option.generator - STRING
     header.option.version - STRING

man/osmium-getid.md

@@ -74,7 +74,7 @@ This command will not work with negative IDs.
 
 -i, --id-file[=FILE]
 :   Read IDs from text file instead of from the command line. Use the special
-    name "-" to read from *stdin*. Each line of the file must start with an
+    name "-" to read from *STDIN*. Each line of the file must start with an
     ID in the format described above. Lines can optionally contain a space
     character or a hash sign ('#') after the ID. This character and all
     following characters are ignored. (This allows files in OPL format to be
@@ -122,7 +122,7 @@ IDs it needs in main memory.
 
 # EXAMPLES
 
-Output nodes 17 and 1234, way 42, and relation 111 to *stdout* in OPL format:
+Output nodes 17 and 1234, way 42, and relation 111 to STDOUT in OPL format:
 
     osmium getid -f opl planet.osm.pbf n1234 w42 n17 r111
 

man/osmium-show.md

@@ -11,7 +11,7 @@ osmium-show - show OSM file
 
 # DESCRIPTION
 
-Show the contents of the *OSM-FILE* on *stdout*, usually in a pager. The
+Show the contents of the *OSM-FILE* on STDOUT, usually in a pager. The
 output format can be set using the **-f**, **output-format** option, its
 shortcuts **-d** (debug format with colors), **-o** (OPL), or **-x** (XML),
 or the `OSMIUM_SHOW_FORMAT` environment variable.

man/output-options.md

@@ -15,7 +15,7 @@
     version of osmium.
 
 -o, --output=FILE
-:   Name of the output file. Default is '-' (*stdout*).
+:   Name of the output file. Default is '-' (STDOUT).
 
 -O, --overwrite
 :   Allow an existing output file to be overwritten. Normally **osmium** will