When joining multiple lines of text into a single line of delimiter-separated fields, the line length can silently violate Shell buffer sizes. The construct:
 echo `grep -l foo *`
causes Shell to strip the newlines from the subshell executed within the grave accents, replacing them with spaces;  '''echo''' posts the result to StandardOutput. One can then use '''sed''' to transform the spaces into a delimiter of choice:
 echo `grep -l foo *` | sed 's/ /:/g'
However, this can lead to lines of unbounded length, which can break Shell buffer limitations. The command will create truncated output when the buffer exceeds the line buffer length in '''sed(1)'''.

'''Therefore:'''

when joining multiple lines of text into a single line with a one character separator, the '''paste(1)''' program should be used instead of 
'''sed(1)''' if the length of the line is unbounded.  Use:
 grep -l foo * | paste -sd':' -
to avoid truncated lines.
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CategoryUnixShellPattern