Intro To 'install' Command In Linux

2023-05-29 - By Robert Elder

I use the 'install' command to copy and install files exactly how I want:

install my-file.txt

Using The 'install' Command Just Like The 'cp' Command

The simplest use of the 'install' command works just like the 'cp' command, and all it does is make a copy of a file. If I start out with the file 'notes.txt':

ls

notes.txt

and run this install command:

install notes.txt notes_copy.txt

you can see that a copy of the file has been created:

ls

notes_copy.txt  notes.txt

Directly Setting Permissions With The 'install' Command

The 'install' command also lets you directly set the permissions on the new copied file. For example, this command will grant all permissions on the copied file:

install --mode='ugo=rwx' notes.txt notes_copy.txt

ls -l notes_copy.txt

-rwxrwxrwx 1 robert robert 0 May 26 11:16 notes_copy.txt

and this command will grant none of them:

install --mode='ugo=-rwx' notes.txt notes_copy.txt

ls -l notes_copy.txt

---------- 1 robert robert 0 May 26 11:18 notes_copy.txt

The Purpose Of The 'install' Command

The primary application of the 'install' command is for use in Makefiles. For example, if we take a look at the Makefile for the 'ncurses' application as well as the configure script, you can see that it creates some variables that reference the 'install' command:

...
configure:3812  if test "${ac_cv_path_install+set}" = set; then
configure:3813    INSTALL=$ac_cv_path_install
configure:3814  else
...

...
Makefile.in:71 INSTALL		= @INSTALL@
Makefile.in:72 INSTALL_PROGRAM	= @INSTALL_PROGRAM@
Makefile.in:73 INSTALL_SCRIPT	= @INSTALL_SCRIPT@
Makefile.in:74 INSTALL_DATA	= @INSTALL_DATA@
...

The 'install' command is used in various places throughout the project's makefiles, specifically during the execution of the make install rule:

...
progs/Makefile.in:218 install.progs: $(AUTO_SRC) $(PROGS) $(DESTDIR)$(bindir)
progs/Makefile.in:219 @MAKE_TERMINFO@	$(LIBTOOL_INSTALL) $(INSTALL_PROG) tic$x     $(DESTDIR)$(bindir)/$(actual_tic)
progs/Makefile.in:220 @MAKE_TERMINFO@	$(LIBTOOL_INSTALL) $(INSTALL_PROG) toe$x     $(DESTDIR)$(bindir)/$(actual_toe)
progs/Makefile.in:221 @MAKE_TERMINFO@	@echo "linking $(actual_infotocap) to $(actual_tic)"
progs/Makefile.in:222 @MAKE_TERMINFO@	-@rm -f $(DESTDIR)$(bindir)/$(actual_infotocap)
progs/Makefile.in:223 @MAKE_TERMINFO@	( cd $(DESTDIR)$(bindir) && $(LN_S) $(actual_tic) $(actual_infotocap) )
progs/Makefile.in:224 @MAKE_TERMINFO@	@echo "linking $(actual_captoinfo) to $(actual_tic)"
progs/Makefile.in:225 @MAKE_TERMINFO@	-@rm -f $(DESTDIR)$(bindir)/$(actual_captoinfo)
progs/Makefile.in:226 @MAKE_TERMINFO@	( cd $(DESTDIR)$(bindir) && $(LN_S) $(actual_tic) $(actual_captoinfo) )
progs/Makefile.in:227 	$(LIBTOOL_INSTALL) $(INSTALL_PROG) infocmp$x $(DESTDIR)$(bindir)/$(actual_infocmp)
progs/Makefile.in:228 	$(LIBTOOL_INSTALL) $(INSTALL_PROG) clear$x   $(DESTDIR)$(bindir)/$(actual_clear)
progs/Makefile.in:229 	$(LIBTOOL_INSTALL) $(INSTALL_PROG) tabs$x    $(DESTDIR)$(bindir)/$(actual_tabs)
progs/Makefile.in:230 	$(LIBTOOL_INSTALL) $(INSTALL_PROG) tput$x    $(DESTDIR)$(bindir)/$(actual_tput)
progs/Makefile.in:231 	$(LIBTOOL_INSTALL) $(INSTALL_PROG) tset$x    $(DESTDIR)$(bindir)/$(actual_tset)
...

Using The 'install' Command To Strip Debug Symbols

As described above, the 'install' command can be used to copy files, but it also contains a number of other features that are useful when installing programs. For example the '-s' flag will strip debug symbols from an executable as it gets copied. Here, I have a simple C program:

int main(){
        return 0;
}

If I compile this program:

gcc -g main.c

and use two different 'install' commands to create copies of the executable:

install -s a.out no-sym.out
install a.out with-sym.out

you can see the 'with-sym.out' that copied without the '-s' flag still has all of its debug symbols:

vim -d <(objdump -t a.out) <(objdump -t with-sym.out)

but the one 'no-sym.out' that copied with the '-s' flag no longer has its debug symbols:

vim -d <(objdump -t a.out) <(objdump -t no-sym.out)

The only difference between the two executables above is the omitted debug symbols that were stripped by the 'install' command.

And that's why the 'install' command is my favourite Linux command.

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