pages*: replaced cat with shell redirection (linux)

pages/linux/mpg123.md

@@ -9,7 +9,7 @@
 
 - Play the mp3 from `stdin`:
 
-`cat {{file.mp3}} | mpg123 -`
+`mpg123 - < {{file.mp3}}`
 
 - Jump forward to the next song:
 

pages/linux/speedread.md

@@ -6,15 +6,15 @@
 
 - Read a text file at a specific speed:
 
-`cat {{path/to/file.txt}} | speedread -wpm {{250}}`
+`speedread -wpm {{250}} < {{path/to/file.txt}}`
 
 - Resume from a specific line:
 
-`cat {{path/to/file.txt}} | speedread -resume {{5}}`
+`speedread -resume {{5}} < {{path/to/file.txt}}`
 
 - Show multiple words at a time:
 
-`cat {{path/to/file.txt}} | speedread -multiword`
+`speedread -multiword < {{path/to/file.txt}}`
 
 - Slow down by 10% during the reading session:
 

pages/linux/xauth.md

@@ -29,7 +29,7 @@
 
 - Merge the authorization entries from a specific file into the authorization database:
 
-`cat {{path/to/file}} | xauth merge -`
+`xauth merge - < {{path/to/file}}`
 
 - Display help:
 

pages/linux/xsel.md

@@ -9,7 +9,7 @@
 
 - Use the contents of a file as input of the clipboard:
 
-`cat {{path/to/file}} | xsel {{[-ib|--input --clipboard]}}`
+`xsel {{[-ib|--input --clipboard]}} < {{path/to/file}}`
 
 - Output the clipboard's contents into the terminal (equivalent to `<Ctrl v>`):