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The sed FAQ
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6.6. Known limitations among sed versions

Limits on distributed versions, although source code for most versions of free sed allows for modification and recompilation. As used below, "no limit" means there is no "fixed" limit. Limits are actually determined by one's hardware, memory, operating system, and which C library is used to compile sed.

6.6.1. Maximum line length
      GNU sed:        no limit
      ssed:           no limit
      sedmod v1.0:    4096 bytes
      HHsed v1.5:     4000 bytes
      sed v1.6:       [pending]
6.6.2. Maximum size for all buffers (pattern space + hold space)
      GNU sed:        no limit
      ssed:           no limit
      sedmod v1.0:    4096 bytes
      HHsed v1.5:     4000 bytes
      sed v1.6:       [pending]
6.6.3. Maximum number of files that can be read with read command
      GNU sed v3+:    no limit
      ssed:           no limit
      GNU sed v2.05:  total no. of r and w commands may not exceed 32
      sedmod v1.0:    total no. of r and w commands may not exceed 20
      sed v1.6:       [pending]
6.6.4. Maximum number of files that can be written with 'w' command
      GNU sed v3+:    no limit (but typical Unix is 253)
      ssed:           no limit (but typical Unix is 253)
      GNU sed v2.05:  total no. of r and w commands may not exceed 32
      sedmod v1.0:    10
      HHsed v1.5:     10
      sed v1.6:       [pending]
6.6.5. Limits on length of label names
      GNU sed:        no limit
      ssed:           no limit
      HHsed v1.5:     no limit
      sed v1.6:       [pending]
      BSD sed:        8 characters

Note that GNU sed and ssed both consider a semicolon to terminate a label name.

6.6.6. Limits on length of write-file names
      GNU sed:        no limit
      ssed:           no limit
      HHsed v1.5:     no limit
      sed v1.6:       [pending]
      BSD sed:        40 characters
6.6.7. Limits on branch/jump commands
      GNU sed:        no limit
      ssed:           no limit
      HHsed v1.5:     50
      sed v1.6:       [pending]

As a practical consequence, this means that HHsed will not read more than 50 lines into the pattern space via an N command, even if the pattern space is only a few hundred bytes in size. HHsed exits with an error message, "infinite branch loop at line {nn}".

The sed FAQ
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   Reprinted courtesy of Eric Pement. Also available at https://sed.sourceforge.net/sedfaq.html Design by Interspire