The original files' contents, mode (permissions), timestamp, owner, and group are preserved in the archive, and may be reconstituted on extraction.
GNU ar can maintain archives whose members have names of any length; however, depending on how ar is configured on your system, a limit on member-name length may be imposed (for compatibility with archive formats maintained with other tools). If it exists, the limit is often 15 characters (typical of formats related to a.out) or 16 characters (typical of formats related to coff).
ar is considered a binary utility because archives of this sort are most often used as libraries holding commonly needed subroutines.
ar will create an index to the symbols defined in relocatable object modules in the archive when you specify the modifier `s'. Once created, this index is updated in the archive whenever ar makes a change to its contents (save for the `q' update operation). An archive with such an index speeds up linking to the library, and allows routines in the library to call each other without regard to their placement in the archive.
You may use `nm -s' or `nm --print-armap' to list this index table. If an archive lacks the table, another form of ar called ranlib can be used to add just the table.
ar insists on at least two arguments to execute: one keyletter specifying the operation (optionally accompanied by other keyletters specifying modifiers), and the archive name to act on.
Most operations can also accept further files arguments, specifying particular files to operate on.
If you wish, you may begin the first command-line argument with a dash.
The p keyletter specifies what operation to execute; it may be any of the following, but you must specify only one of them:
If you specify the `v' modifier, ar will list each module as it is deleted.
The ordering of members in an archive can make a difference in how programs are linked using the library, if a symbol is defined in more than one member.
If no modifiers are used with m, any members you name in the files arguments are moved to the end of the archive; you can use the `a', `b', or `i' modifiers to move them to a specified place instead.
If you specify no files, all the files in the archive are printed.
The modifiers `a', `b', and `i' do not affect this operation; new members are always placed at the end of the archive.
The modifier `v' makes ar list each file as it is appended.
Since the point of this operation is speed, the archive's symbol table index is not updated, even if it already existed; you can use `ar s' or ranlib explicitly to update the symbol table index.
If one of the files named in files doesn't exist, ar displays an error message, and leaves undisturbed any existing members of the archive matching that name.
By default, new members are added at the end of the file; but you may use one of the modifiers `a', `b', or `i' to request placement relative to some existing member.
The modifier `v' used with this operation elicits a line of output for each file inserted, along with one of the letters `a' or `r' to indicate whether the file was appended (no old member deleted) or replaced.
If you do not specify any files, all files in the archive are listed.
If there is more than one file with the same name (say, `fie') in an archive (say `b.a'), `ar t b.a fie' will list only the first instance; to see them all, you must ask for a complete listing---in our example, `ar t b.a'.
If you do not specify any files, all files in the archive are extracted.
A number of modifiers (mod) may immediately follow the p keyletter, to specify variations on an operation's behavior:
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