Add --output-file flag for writing values to file

configure.ac

@@ -40,6 +40,7 @@ if test "$USE_MAINTAINER_MODE" = yes; then
 fi
 
 AC_CHECK_FUNCS(memmem)
+AC_CHECK_FUNCS(mkstemp)
 
 AC_CHECK_HEADER("sys/cygwin.h", [have_cygwin=1;])
 AC_CHECK_HEADER("shlwapi.h",[have_shlwapi=1;])

docs/content/manual/dev/manual.yml

@@ -227,6 +227,25 @@ sections:
         like awk's -f option. This changes the filter argument to be
         interpreted as a filename, instead of the source of a program.
 
+      * `-o` / `--output-file filename`:
+
+        Write output values to the named file instead of standard out.
+        The output is first written to a temporary file in the same
+        directory, then renamed into place on success.  This makes it
+        safe to use an input file as the output file (e.g.,
+        `jq '.x += 1' f.json -o f.json`).
+
+        The outputs from `--debug-dump-disasm` and `--debug-trace` are
+        still written to standard out, so this option can be used to
+        separate them.
+
+      * `-O` / `--clobber-output filename`:
+
+        Like `-o`, but truncates the output file immediately instead
+        of writing to a temporary file first.  This is faster, but
+        the output file must not also be an input file, and partial
+        output may be left behind if jq is interrupted.
+
       * `-L directory` / `--library-path directory`:
 
         Prepend `directory` to the search list for modules.  If this